Some of the children are foreigners whose parents brought them to be raised under Islamic State rule, or child fighters conscripted into what the group dubbed "cubs of the caliphate."

The report said that more than 4,600 foreign minors were affiliated with ISIS, including an estimated 14 Canadian citizens.

In a classroom of the University of Mosul, around 50 volunteers have undergone a week's training on how to combat the jihadists' ideology.