>> NARRATOR: Tonight on this special edition of Frontline... >> The French launching air strikes against ISIS targets... >> NARRATOR: As the fight against ISIS intensifies after the Paris terror attacks, an exclusive report on how the radical group is spreading.

Correspondent Najibullah Quraishi shows us for the first time ISIS's new foothold in Afghanistan.

>> QURAISHI: Their aim is to have their networks all over the world.

When I saw these young children who learn how to kill people, how to do jihad, I was thinking, "The war will never end."

>> NARRATOR: And later tonight, in Pakistan, the Taliban are wreaking havoc in Karachi with crime, kidnapping, and targeted assassinations.

>> Could you point out the areas where the Taliban has a strong presence?

>> NARRATOR: Frontline is with the police unit hunting the Taliban.

Tonight, two new reports, one exclusive hour of Frontline.

>> NARRATOR: Journalist Najibullah Quraishi is heading into dangerous territory in Kunar Province, eastern Afghanistan.

For more than a decade, Najibullah has covered the war between the Taliban and the American-led coalition.

Now he is investigating a new story.

>> QURAISHI: I have been embedded with the Taliban many, many times.

But when I first heard about ISIS in Afghanistan, I was shocked.

I was thinking, "Why ISIS in Afghanistan?

What they are doing in my country?"

They're completely different than the Taliban.

They are not after one country or one place or one district.

Their aim is to have their groups, to have their networks all over the world.

>> NARRATOR: As ISIS has been fighting for control of territory in Iraq and Syria, it has announced branches and affiliates in at least nine other countries.

For the past year, it's been gaining ground in Afghanistan.

But no journalist has been able to get inside ISIS territory here and film them in action.

The group is notorious for its kidnappings and brutal executions.

>> QURAISHI: I was waiting for over eight months to get access to ISIS.

I was very excited as a journalist that I was going to meet this group, but I was remembering my wife, my sons.

Then I was thinking, "Maybe you won't come back again.

"They might kill you, they might kidnap you, they might do something wrong."

>> NARRATOR: Najibullah arrives in the district of Shaigal.

This was once Al Qaeda and Taliban territory.

ISIS gunmen seized control a year ago.

Abu Rashid, the most senior commander in the village, used to be a member of the Taliban.

But in 2014, after ISIS declared an Islamic state, or caliphate, in Iraq and Syria, he defected.

>> (translated): Yes, we were fighting holy war as Taliban.

Our holy war was just, because there was no caliphate then.

But God says when there is a caliphate, you must join the caliphate.

There is a caliphate now, so we have left the Taliban.

We are fighting holy war under Caliph's leadership.

We want the Islamic system all over the world, and we will fight for it.

>> NARRATOR: Though still small in number, ISIS now claims to control territory in several districts across Eastern Afghanistan, especially in the provinces of Kunar and Nangarhar.

Many fighters have defected from other groups because ISIS pays more.

>> QURAISHI: The commander told me ISIS offering them $700 per month.

Once they join ISIS, they get a normal salary.

And they can feed their families.

Afghanistan is a poor country, and they have to do something, they have to work something, and $700 is a lot in Afghanistan.

>> NARRATOR: Here, ISIS fighters live among the locals and seem to control every aspect of village life.

They take local wives, collect taxes, and even run the village school.

The fighters say that all local children are educated by the Islamic State from the age of three.

>> NARRATOR: The teacher, Abdullah, spends a few minutes explaining the theory of jihad, or holy war.

Then he moves on to its practice.

>> NARRATOR: When the children struggle with his questions, the teacher whispers the answers.

(hammer clicks) (Abdullah giving instructions) (hammer clicks) (hammer clicks) >> (translated): Sharia law tells us that children should be given all essential skills.

So we teach them and give them military training to prepare them in mind and body.

So they are set on the right path, and each generation will learn and teach in turn.

>> (translated): Yes, of course it's right, as we see from the Prophet's young companions.

Those companions were vying with each other to take up arms.

So this enthusiasm, spirit, and desire is in our children, and in our women, too.

Time will show what we can do for God's religion.

We are always ready to sacrifice for it.

>> NARRATOR: In the fields, the gunmen spread out to avoid attracting attention from American drones.

They say that several hundred Afghan ISIS fighters have been killed in targeted strikes since July.

The commanders carefully choreograph their interviews with Najibullah.

Their message is clear: the Taliban are puppets of Pakistan, whereas ISIS answers only to God.

>> (translated): The Taliban take their orders from Pakistani intelligence.

Those people don't accept the caliphate.

But we are free, and our aim is only to seek God's happiness.

We want Islamic law on earth.

We answer to no one.

We welcome the caliphate.

>> NARRATOR: No one knows for sure how many fighters ISIS has in Afghanistan.

Afghan officials estimate there are currently 1,000, and that the number is growing.

According to commander Abu Rashid, they are also attracting jihadists from around the world.

>> (translated): Yes, thank God, there are foreign fighters across the region.

Many have joined us from overseas.

They have come from Saudi Arabia and Europe.

But you can't speak to them now.

>> NARRATOR: Suddenly, the commanders tell Najibullah he has to leave.

They see his presence as a security threat.

The story of ISIS in Afghanistan begins with an execution.

In June 2014, 12 Taliban commanders in the province of Nuristan were captured and killed by a group of masked men.

At the time, nobody knew who the killers were.

>> QURAISHI: That group was ISIS.

They were no one else, they were ISIS.

They were just showing their power.

It was their first threat to show the Taliban, "We are much more powerful than you guys and we are much worse than you guys."

>> NARRATOR: Najibullah has now crossed into Taliban-held territory.

He's arranged to meet a senior commander for Kunar Province.

A foot-soldier guides him to the Taliban hideout in a forest just 15 miles from the ISIS-controlled village.

For more than a decade, Mowlavi Samad has led the Taliban's fight against the U.S. and its allies in this district.

Now he's fighting on another front: against ISIS.

>> (translated): We do not agree with those who want ISIS here in Afghanistan.

We don't agree because under the Taliban, we are already Islamic.

There is no power vacuum here, so why start using this name?

Some of our brother Taliban have become dissatisfied and raised their flags against us.

But we pray that the faithful won't take part in this war, because it's divisive.

The Prophet Muhammad said, "Wherever there is intrigue, don't get involved!"

>> NARRATOR: These Taliban fighters face an uncertain future.

In July 2015, the movement announced the death of its founder and leader, Mullah Omar.

Off camera, some of the insurgents in this village tell Najibullah they are now thinking of defecting.

>> QURAISHI: They're saying in the coming future, there will be no Taliban anymore.

They would be all joining ISIS.

>> NARRATOR: The Taliban remain by far the most powerful militant group in Afghanistan.

(gunfire) But the ISIS campaign against them is brutal.

(people singing in video) Last summer, ISIS drove the Taliban out of Achin district in in the eastern province of Nangarhar.

Ten village elders, some of whom were Taliban, were then taken to a remote hillside and forced to kneel on explosives.

>> QURAISHI: The first time when I saw that propaganda video, I was thinking, "What they are doing?

Why are they so harsh, why are they so crazy?"

I never seen before something like this.

Not in the Taliban time, in the government, or other insurgency in Afghanistan.

Never.

It was horrible to watch.

(loud explosion) >> NARRATOR: Since ISIS began gaining ground in eastern Afghanistan, more than 17,000 families are thought to have fled their homes.

>> (translated): This is our home now.

We brought the animals with us.

>> NARRATOR: Until recently, Agh Jan and his family lived in the district of Achin, near the hillside where ISIS killed the group of elders.

>> (translated): People's lives used to be good in our district.

It was very peaceful.

Then all these fighters appeared.

They made life bitter for local people.

>> (translated): At first they were all together, but then they split.

Some went to Islamic State and others to the Taliban.

They became enemies.

Their fighting hurt lots of ordinary people.

Now the situation is terrible.

Neither the Taliban nor the Islamic State care about ordinary Afghans.

Whichever group is in control, they beat us.

We really don't know one from another.

You can't stand up to them.

If you try, they come in the night and kill you with your children.

Your children will be made to watch as you are beheaded.

>> NARRATOR: After ISIS took control of his village, Agh Jan and his family decided to flee to the city of Jalalabad.

Other parents begged him to take their children with him.

>> (translated): We got a truck at night and put all the children in.

These are all little kids.

We accept all the hardship for their sake.

Our lives are wrecked, but at least these children might have a future.

(car honking) >> NARRATOR: Najibullah is on the road again.

He's traveling through Nangarhar province, just a few miles from the Pakistan border.

The Taliban and ISIS may be fighting each other here, but they have a common enemy-- the Afghan government.

Since the U.S. began withdrawing troops in 2011, Afghan forces have struggled to contain the Taliban, who are now in control of several key districts across the country.

And this fall, ISIS fighters began to launch direct attacks on government outposts here.

Najibullah has arranged to accompany a local police unit on the front lines.

>> (translated): This area is called Khir-abaad.

We are here to search and destroy.

The enemy is over there.

>> NARRATOR: Mali Mohammad Alam leads a 25-man police militia.

Resources and equipment are scarce.

Enemy lines are just a few hundred yards away.

>> (translated): The government pays our salary, but they don't supply us.

We bought the rockets ourselves, in cash.

We buy the bullets and everything.

We aren't given a budget for it.

We buy them from the boys' wages-- the rockets, bullets, everything.

>> NARRATOR: The chief says he is willing to use brutal tactics against the Taliban and ISIS.

>> (translated): We captured two people yesterday.

They were spies.

We tortured them a bit.

The human rights people tell us not to.

But if we don't torture or beat them, how can we get anything out of them?

The human rights people should let us torture them or finish them off.

Otherwise our job is impossible.

>> NARRATOR: The locals tell Najibullah they see little difference between the police and the insurgents.

>> (translated): We are fed up, the children are fed up, the women are fed up.

>> (translated): To be honest, none of them.

If we say anything about any of them, they'll come and get us.

I swear to God we're fed up with all of them, you know?

They'll just drag you outside and beat you until blood comes out of your nose.

>> NARRATOR: Suddenly, the visit comes to a halt.

>> (translated): I can't take you any further.

The enemy is nearby and you are unarmed.

We could run into the enemy at any time, you never know.

That is enemy territory.

We'll take you back to your car.

>> (translated): Yes, it's dangerous to take you any further.

We might not get you back alive.

>> NARRATOR: Najibullah has made contact with another ISIS cell.

>> NARRATOR: Chapa Dara district used to be home to the Taliban and Al Qaeda fighters loyal to Osama bin Laden.

Now it is home to ISIS.

The commander here is named Mawlawi.

A few weeks ago, he declared this district part of the global Islamic State.

>> (translated): Now ISIS is here, and by God's will, it's spreading.

Since we started doing jihad, no American has come to this area.

No heretics come here.

This area is under our control.

We aim to bring the Islamic system to Kunar, across Afghanistan, and even the world.

>> NARRATOR: Commander Mawlawi tells Najibullah he must come with him deeper into ISIS territory.

>> QURAISHI: I didn't know where we were going.

If they decided to hurt me or kidnap me, there was nothing I could do.

I honestly didn't know if I was going to get back.

>> NARRATOR: After an hour of walking, the commander introduces Najibullah to two teenagers-- Bashrullah, who is 13, and Naimatullah, who is 17.

He says they are training to be ISIS suicide bombers.

>> (translated): I told the elders a year ago that I wanted to do it, and I'm ready whenever they give the order.

I'm ready now, God willing.

>> NARRATOR: The fighters here say they are focused on attacking the Afghan government, not the Taliban.

The commander says he wants to use the two teens to kill a pro-government warlord named Jandad.

>> (translated): I'll kill Jandad in Kunar and avenge the blood of our fighters.

>> (translated): He is a heretic and a slave of infidels.

He serves them.

He killed our fighters, he jailed my friends, and killed prisoners.

>> (translated): Yes, I have.

>> (translated): Yes, I have practiced that.

My commanders showed me how.

>> (translated): Here in Afghanistan.

>> (translated): They're foreigners.

>> NARRATOR: Najibullah presses the boys about their foreign trainers.

>> NARRATOR: But it seems to be a sensitive subject.

>> NARRATOR: The boys tell Najibullah they are ready to carry out their suicide mission as soon as the order comes.

>> (translated): I want to do this for Allah, and to avenge our fighters against the unbelievers.

Our commanders get their orders from ISIS.

If they prepare a car bomb, wherever they say do it, I will do it.

>> (translated): Yes.

>> (translated): No.

We're here in Afghanistan.

We see all the fighters.

We learn from them.

God willing, we want to be like them!

(bird squawking) >> NARRATOR: In the ISIS-held district of Shaigal, the group is using many techniques to groom young children to fight and die for the Islamic State.

>> NARRATOR: The fighters tell Najibullah they receive propaganda videos directly from ISIS in Syria and Iraq.

They say they show the videos to the village children every day.

>> QURAISHI: I was asking them why they are watching in front of these young children?

They said they should learn, they should know from now, and it's normal for them.

>> NARRATOR: The videos don't just show attacks and atrocities.

This an ISIS military school for children, somewhere in the Middle East.

(gunfire) >> QURAISHI: All these videos, they're just telling them how to kill people, how to behead, and how to become suicide bombers.

And their main thing is to kill infidels.

This is their aim, and they are clearly telling, "This is in Quran."

So what does the child believe?

What does he think?

He thinks, "Yes, I am Muslim, and he's telling me the truth."

>> NARRATOR: Najibullah films the Afghan children copying what they've just watched.

>> QURAISHI: When I saw these young children, I was really, really upset, really sad.

I was thinking about Afghanistan future.

Afghanistan's next generation.

What we have next?

These children who learn how to kill people, how to do Jihad, how to behead, how to fire?

This would be Afghanistan?

I was thinking maybe the war will never end.

Never.

And the people will keep suffering from war.

>> NARRATOR: ISIS in Afghanistan may still be in its infancy, but the movement has already shown how quickly it can grow.

And its commanders here have grand ambitions for the next generation of ISIS soldiers.

>> (translated): The Garden of the Caliphate wants a river of blood from us.

Faith and belief demand blood.

You must sacrifice to gain eternal life.

God will expand this beautiful caliphate everywhere.

>> NARRATOR: Coming up next, across the border in Pakistan, Frontline is with a police unit fighting terrorism.

>> These Taliban members sound the alarm to tell people in the area that the police are here.

>> NARRATOR: In the streets of Karachi... >> You can see these two guys being shot, and shots being fired on them.

>> NARRATOR: ...the battle against the Taliban.

>> They were trained for traditional policing, but it is not traditional policing.

They are fighting terrorism.

They are fighting a full-fledged war.

>> NARRATOR: Starting right now, "The Taliban Hunters."

>> NARRATOR: Karachi, Pakistan.

Officer Ijaz Bajwa heads the city's counter-terrorism police unit.

His team is on the front line of an escalating war with the Pakistani Taliban.

>> NARRATOR: Officer Ijaz has received a tip that two militants are planning an attack from a hideout in Karachi's slums.

Reporter Mobeen Azhar is accompanying the police on the raid.

>> NARRATOR: The unit is informally known as the Taliban Hunters.

>> NARRATOR: The Pakistani Taliban, or TTP, used to have only a small underground presence in Karachi.

Most of its fighters were based in the remote tribal areas near the Afghan border.

But over the last few years, they have been gaining ground here in the country's commercial capital-- a city of over 20 million people.

The team is heading into one of the most notorious slums: Ittehad Town, a TTP stronghold.

>> NARRATOR: The team enters Ittehad Town in the early hours of the morning.

The streets are empty.

The final approach towards the target house is on foot.

(dogs barking) >> NARRATOR: The police say if they are spotted entering the slums, Taliban watchmen often sound an alarm as a call to arms for local militants.

No one knows how many men are inside and who could be watching.

(gunshots) >> NARRATOR: The suspects open fire.

(gunshots) >> NARRATOR: The priority now is getting out of the slum.

(bell ringing) >> So there was gunshots fired.

And they took a gun magazine from one of the suspects.

They're now taking him to the compound.

As soon as we got in there, there was the sound of a kind of an alarm.

And a few of the officers told me that these Taliban members sound the alarm to tell people in the area that the police are here.

That's why we have to make a quick exit right now.

We have to get out of the area.

(siren wailing) >> NARRATOR: The police say they believe the suspects were in the final stages of planning to kidnap a prominent businessman.

They'll be put in solitary confinement for the next five days.

Human rights groups have accused the Karachi authorities of abusing the militants they capture in the fight against the Taliban.

Officer Ijaz says he operates within the law, but that the harsh conditions in his jail make suspects more likely to talk.

The Pakistani Taliban first emerged in 2007.

Their violent campaign to topple the government made headlines last year with the attack on a school in Peshawar that left 132 children dead.

(sirens wailing) >> This was a well-planned massacre-- a bloody eight-hour rampage executed without mercy.

(man crying) >> NARRATOR: Over the last 18 months, the Pakistani army has been trying to force the Taliban out of their sanctuary in North Waziristan, a remote region near the Afghan border.

The military campaign has had an unintended consequence.

Thousands of Taliban have taken refuge in the slums of Karachi.

They use the city as a base to raise money through crime and kidnapping, and to launch more attacks.

The battle against the militants here falls mainly to the police, not the army.

Officer Ijaz and his team monitor the Taliban and other extremist groups from this surveillance center.

>> Could you point out the areas where the Taliban has a strong presence?

>> Urangi, Baldir, Saeedabad, Ittehad Town.

These areas.

Then we have Surjani, we have Sarabghot area.

So basically the slums are encircling the city, and these slums, they are very dangerous.

>> NARRATOR: It's from these slums that the Taliban have been organizing their attacks.

>> Please show us the blast.

This white bus with blue stripes, this is coming.

And here you go.

>> NARRATOR: This suicide bombing was carried out at rush hour in a busy marketplace.

Police say six people were killed and 52 injured.

But the militants' most common tactic is targeted assassination.

>> You can see these two guys being shot.

Shots being fired on them.

>> NARRATOR: Here, two men are gunned down by Taliban members on motorbikes.

One is killed instantly.

Police, journalists, and anyone opposing the Taliban is a potential target.

>> These two guys will fire the next guy going on a motorbike in blue dress.

>> NARRATOR: This man rides his motorbike during rush hour.

His killer is just a few feet behind him.

The gunman strikes and drives away unchallenged.

Officer Ijaz says his men have limited resources to take on the Taliban.

>> NARRATOR: Captured Taliban suspects are detained in Officer Ijaz's compound.

>> This particular suspect, he's in custody on suspicion of killing some of law enforcement personnel.

And we're interrogating him, still some things to extract, because we have some physical and material evidence against him, and we need his confession or his side of the story too for better chance of a conviction.

>> NARRATOR: This man, Mansoor, is accused of multiple targeted assassinations.

Ijaz insists that his face remains covered to stop him from seeing the officers.

He says if Mansoor is ever released, he could try to target the police who questioned him.

Mansoor agrees to be interviewed, but Officer Ijaz stays in the room to monitor what he says.

>> NARRATOR: Ijaz suddenly interrupts to ask his own questions.

>> NARRATOR: Mansoor says he is proud to have killed the police officers.

He's now awaiting trial.

Officer Ijaz says he can hold suspects for up to 28 days for interrogation.

If his team can't extract a confession or get other solid evidence in that time, he has to let them go.

>> I got to the compound about ten minutes ago, and as soon as I got here, I could hear screaming from the interrogation area down there.

You can see two suspects that are up against the wall right now.

>> NARRATOR: It's now five days since the raid and capture of the two Taliban suspects.

Officer Ijaz agrees to bring them out of their cells to be interviewed.

Once again, he insists that their faces are covered, and that he sits in.

>> I need to ask you something, Officer Ijaz.

You know, when I arrived at the compound, I did hear some screaming from one of the interrogation rooms, but the human rights commission of Pakistan has expressed concerns about the use of torture.

What techniques do you use?

>> (laughs) We don't do this, because... >> NARRATOR: Ijaz says that these prisoners have already confessed to a kidnapping plot.

>> NARRATOR: Over the last year, Officer Ijaz says his team has captured more than 200 militants.

Yet terrorist attacks in Karachi continue.

Last May, a Taliban splinter group killed 43 civilians in an attack on a bus.

The killers had recently pledged loyalty to ISIS.

>> Next time... >> This is the al-Qaeda that Osama bin Laden only dreamed of.

>> The intelligence continued to point to what could happen.

>> The view was, this is Iraq's problem, let them deal with it.

>> The growth of ISIS was noted and the deterioration of the Iraqi forces was missed.

>> OBAMA: If you threaten America, you will find no safe haven.

>> Go to pbs.org/frontline to read an interview with filmmaker Najibullah Quraishi about his reporting from inside ISIS territory.

>> I honestly didn't know if I was going to get back.

>> And see more of our ongoing coverage of ISIS.

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