The Syrian Observatory for Human Rights said the children, all aged under 18, were recruited near schools, mosques and in public areas where ISIS carries out killings and brutal punishments on local people.
One such young boy appeared in a video early this month shooting dead an Israeli Arab accused by ISIS of being as spy. A French police source said the boy might be the half-brother of Mohamed Merah, who killed three soldiers, a rabbi and three Jewish children in Toulouse in 2012.
“They use children because it is easy to brainwash them. They can build these children into what they want, they stop them from going to school and send them to ISIS schools instead,” said Rami Abdulrahman, head of the British-based Observatory.
ISIS declared a caliphate last year in territory it controls in Syria and Iraq and is being targeted by U.S.-led air strikes in both countries.
It has beheaded or shot dead Syrian civilians, combatants, foreign aid workers and journalists and has released videos appearing to show children witnessing or participating in some of the killings. The group persecutes people across sects and ethnicities who do not adhere to its ultra-hardline doctrine.
The group may be resorting to children because it has been having difficulties recruiting adults since the start of the year, with only 120 joining its ranks, Abdulrahman said.
This was partly due to tighter controls on the Turkish border, where foreign fighters tend to enter, he added.
ISIS has encouraged parents to send children to training camps or has recruited them without their parents’ consent, often luring them with money, said the Observatory, which tracks the conflict using sources on the ground.
At the training camps, the children learn to fire live ammunition, fight in battles and to drive, it said. ISIS also recruits children as informants and as guards for its headquarters as well as welcoming children with birth defects into its ranks, the Observatory added.