In this photo released April 25, 2015, by a militant website, young boys take part in a parade after graduating from a religious school in Islamic State-controlled Tal Afar, near the Iraqi city of Mosul. (Militant website via AP)

The boy burst into tears as police apprehended him after he was spotted nervously pacing up and down a street in the Iraqi city of Kirkuk. When they cut open the Barcelona soccer shirt he was wearing, they found a suicide belt.

He was just 15, according to local officials.

Footage broadcast Monday on Kurdish television stations showed the dramatic moments as security forces gingerly stripped him of his explosives-laden belt. Tragedy was averted Sunday evening, but numerous young bombers have carried out attacks in recent months, as the Islamic State militant group has enlisted children in suicide missions.

The same evening that police foiled the Kirkuk attack, a suicide bomber of about the same age struck outside a Shiite mosque in the city, killing six people, security forces said.

The devastating bombing at a wedding in southeastern Turkey that killed at least 50 people late Saturday was also initially thought to have been carried out by a child.

In March, a suicide bomber who appeared to be no older than 15 or 16 struck at a youth soccer match in the southern Iraqi village of Asriya, killing 43 people, many of them children.

Although the Islamic State, also known as ISIS, does not reveal the age of its operatives as it heralds its bombing campaigns, the faces of many look years away from adulthood.

Analysts say it is one of the consequences of the Islamic State’s campaign of indoctrination. The United States estimates that U.S. and coalition jets have killed 45,000 Islamic State militants since an air campaign began two years ago. The “cubs of the caliphate,” as the Islamic State labels its child fighters, are being used to fill the gap.

“This is a product of ISIS’s investment in children,” said Hassan Hassan, co-author of “ISIS: Inside the Army of Terror” and resident fellow at the Tahrir Institute for Middle East Policy. “The second generation of ISIS is already happening. When they need them, they can call on them.”

In its early days, the Islamic State — an outgrowth of al-Qaeda in Iraq and formerly known as the Islamic State of Iraq and Syria — held family-fair-style events in Syria, complete with games and ice-cream-eating competitions. As it gained territory, it opened training camps and schools.

Textbooks found in areas formerly controlled by the Islamic State offer a glimpse of the hard-line version of Islam it teaches. Young Yazidi boys who were kidnapped en masse along with their mothers and sisters as Islamic State militants captured the Iraqi town of Sinjar two years ago have been forced to undergo military training, according to those who have escaped.

A person shows pieces of projectile near the scene of an attack on a wedding party that left at least 30 dead in Gaziantep in southeastern Turkey. (Ilyas Akengin/AFP/Getty Images)

“If people join bringing their children, it’s preferable to ISIS,” Hassan said. “Their brains are like a whiteboard they can write on.”

The group’s methods echo those of al-Qaeda in Iraq, which also used child suicide bombers, whom it called the “Birds of Paradise.” The Taliban also has used child bombers in Afghanistan and Pakistan to gain access to sensitive targets without arousing suspicions.

In Iraq, freedom of movement can be restrictive for young men of fighting age — especially anyone traveling from restive areas near Islamic State territory.

“It’s easier for children to infiltrate,” said Brig. Gen. Sarhad Qadir, a commander with the Kirkuk police. He said the boy who was detained in Kirkuk may have been drugged.

“He was scared and crying and wasn’t acting normally,” Qadir said, adding that he appeared dazed.

He is being interrogated and said he traveled to Kirkuk from the Islamic State-held city of Mosul but is “not 100 percent” fine mentally, Qadir said.

In Turkey, President Recep Tayyip Erdogan initially said that the bomber at a wedding in the city of Gazientep on Saturday was 12 to 14 years old. However, Prime Minister Binali Yildirim said Monday that authorities were still trying to identify the bomber and did not know whether he was “a child or a grown-up,” the Associated Press reported. Earlier statements apparently had been a “guess” based on witness testimony.

In any case, the Islamic State appears to be increasingly using young recruits for its most brutal missions. In the Iraqi province of Diyala earlier this year, a mother told authorities that the Islamic State had recruited her 21-year-old and 14-year-old sons and that they were planning a suicide attack. The police distributed their pictures to checkpoints in the area, but the youngest still managed to blow himself up outside a coffee shop.

“Who would suspect a child?” Kirkuk Gov. Najmiddin Karim said. “Sadly, they are brainwashed.”

The Islamic State has lost almost half the territory it once controlled in Iraq and about 20 percent in Syria, according to U.S. estimates. But the strategy of the U.S.-led coalition has drawn criticism, with some saying that its scope is too narrow and that defeating the group militarily is not enough.

Hassan said thousands of children are growing up without an education amid the violence, making them ripe for recruitment by the Islamic State unless social and economic issues are addressed.

“That needs to be done to ensure that there’s no second iteration of ISIS, there’s no comeback,” he said. “Ignoring it is a huge mistake.”

Mustafa Salim in Baghdad contributed to this report.