A quiet middle-class Shiite neighborhood in western Baghdad was transformed recently into a mini-boot camp, training teenagers for battle against the Islamic State group.

The Shiite boys and young men ran through its normally placid streets carrying out mock exercises for urban warfare since the toughest battles against the Sunni extremists are likely to involve street fighting. They were taught how to hold, control and aim light weapons, though they didn't fire them.

In cities from Baghdad to Basra, summer camps set up by the Popular Mobilization Forces, Iraq's largest militia umbrella group, are training teens and boys as young as middle school age after the country's top Shiite cleric issued an edict calling on students to use their school vacations to prepare for battle if they are needed.

With dozens of such camps around the country, hundreds of students have gone through the training though it is impossible to say how many went on to fight the Sunni extremists since those who do so go independently. Of around 200 cadets in a training class visited by The Associated Press, about half were under the age of 18, with some as young as 15. Several said they intended to join their fathers and older brothers on the front lines.

It's yet another way minors are being dragged into Iraq's brutal war as the military, Shiite militias and Kurdish fighters battle to take back territory from Islamic State militants, who seized much of the country's north and west over the past year. The Sunni extremists have aggressively enlisted children as young as 10 for combat, as suicide bombers and as executioners in their horrifying videos.

Among those training this month in the streets of Baghdad, 15-year-old Jaafar Osama said he used to want to be an engineer when he grew up, but now he wants to be a fighter. His father is a volunteer fighting with the Shiite militias in Anbar and his older brother is fighting in Beiji, north of Baghdad.

"God willing, when I complete my training I will join them, even if it means sacrificing my life to keep Iraq safe," he said.

Earlier this summer, the AP saw over a dozen armed young boys, some as young as 10, deployed on the front line with the Shiite militias in western Anbar province.

Baghdad natives Hussein Ali, 12, and his cousin Ali Ahsan, 14, said they joined their fathers on the battlefield after they finished their final exams. Carrying AK-47's, they paced around the Anbar desert, boasting of their resolve to liberate the predominantly Sunni province from IS militants.

"It's our honor to serve our country," Hussein Ali said, adding that some of his schoolmates were also fighting. When asked if he was afraid, he smiled and said no.

The training program could have serious implications for the U.S.-led coalition, which supports the Iraqi government but has distanced itself from the Iranian-backed militias. The U.S. does not work directly with the Popular Mobilization Forces, but they receive weapons and funding from the Iraqi government and are trained by the Iraqi military, which receives its training from the U.S.

The Child Soldiers Prevention Act of 2008 says the U.S. cannot provide certain forms of military support, including foreign military financing and direct commercial sales to governments that recruit and use child soldiers or support paramilitaries or militias that do.

When informed of the AP findings, the U.S. Embassy in Baghdad issued a statement saying the U.S. was "very concerned by the allegations on the use of child soldiers in Iraq among some Popular Mobilization Forces in the fight against ISIL," using an acronym for the militant group. "We have strongly condemned this practice around the world and will continue to do so."

Last year, when IS took over the northern city of Mosul, stormed to the doorstep of Baghdad and threatened to destroy Shiite holy sites, Iraq's top Shiite cleric, Ayatollah Ali al-Sistani, called on the public to volunteer to fight. His influence was so great that hundreds of thousands of men came forward to join the hastily-established Popular Mobilization Forces along with some of the long-established Shiite militias, most of which receive support from Iran.

Then, on June 9, as schools let out, al-Sistani issued a new fatwa urging young people in college, high school and even middle school to use their summer vacations to "contribute to (the country's) preservation by training to take up arms and prepare to fend off risk, if this is required."

A spokesman for the Popular Mobilization Forces, Kareem al-Nouri, said the camps give "lessons in self-defense" and underage volunteers are expected to return to school by September, not go to the front.

A spokesman for the Iraqi prime minister's office echoed that. There may be "some isolated incidents" of underage fighters joining combat on their own, Saad al-Harithi told the AP. "But there has been no instruction by the Marjaiyah (the top Shiite religious authority) or the Popular Mobilization Forces for children to join the battle."

"We are a government that frowns upon children going to war," he said.

But the line between combat training and actually joining combat is weakly enforced by the Popular Mobilization Forces. Multiple militias operate under its umbrella, with fighters loyal to different leaders who often act independently.

Donatella Rovera, Amnesty International's senior crisis response adviser, said that if the Shiite militias are using children as fighters, "then the countries that are supporting them are in violation of the U.N. Convention" on the Rights of the Child.

"If you are supporting the Iraqi army, then by extension, you are supporting" the Popular Mobilization Forces, she said.

The U.N. convention does not ban giving military training to minors. But Jo Becker, the advocacy director of the children's rights division at Human Rights Watch, said that it puts children at risk.

"Governments like to say, 'Of course, we can recruit without putting children in harm's way,' but in a place of conflict, those landscapes blur very quickly," she said.