Last week, the Syrian Observatory for Human Rights reported that more than 50 children fighting for the Islamic State group had died so far this year. Now, an investigation by the Associated Press (AP) has unearthed details of what children training to become “cubs of the caliphate” go through in ISIS-run camps.

The boys, some of them as young as 8, were reportedly shown beheading videos and then asked to decapitate dolls, at one of the training camps run by the militant group.

“The first time I hit it, I couldn’t cut it. Neither the second nor the third time,” a 14-year-old Yazidi boy, identified as Yahya by his captors, told the AP. “Then they taught me how to hold the sword, and they told me how to hit. They told me it was the head of the infidels.”

The Yazidis, whose religious practices resemble an ancient form of Zoroastrianism, have faced intense persecution since ISIS began its onslaught in Iraq last June. In addition to over 5,000 Yazidis -- considered "devil worshippers" by the Sunni ISIS militants -- that have since been killed, hundreds of Yazidi boys have been forcibly converted to Islam and are currently being trained to become jihadists.

The boy, who was among the hundreds kidnapped by ISIS from northern Iraq, managed to escape from the training camp located at the group’s headquarters in the Syrian city of Raqqa. The exact number and locations of ISIS’ training camps is not yet known.

“I knew I wouldn't be able to behead someone like that. Even as an adult,” Yahya, whose real name was not disclosed, told the AP, referring to the beheading videos ISIS militants showed the children. “I was scared when I saw that.”

ISIS is also using children as suicide bombers, the Human Rights Watch reported last week. Although the exact number of child soldiers currently fighting for the militant group is hard to estimate, ISIS is believed to have recruited more than 1,100 children since the beginning of this year.

Over the weekend, ISIS also released a video showing a child beheading a man who identifies himself as a soldier in the army of Syrian President Bashar Assad.

Yahya, who had spent five months at the Farouq camp in Raqqa before escaping in March, said that in addition to being trained for beheading, he was taught verses from Quran and how to shoot someone at close range.

“We [the children] were beating each other because it would make us tougher and they said it wouldn’t hurt next time.” Yahya told the AP, adding that he was also forced to hit his 10-year-old brother as part of the training. “They [ISIS militants] beat us everywhere.”