Children as young as eight are being put on the front line by Islamic State, according to Syrian activists.
Footage obtained by Sky News shows how youngsters play mock execution games.
In one video, they kneel down and pretend to be shot, while in another a toddler tries to behead a teddy bear.
“Those kids are a whole generation that’s lost,” said activist Sarmad al Jilane.
He added: “There are a lot of suicide bombers that Daesh (IS) have orchestrated - as well as brainwashing the children.
“They place them in the front line of battles and if they are killed then they are considered to be protecting Daesh lives.”
The group Raqqa Is Being Slaughtered Silently (RBSS) also warns Russian airstrikes are killing civilians and helping Daesh.
Sarmad, who is co-founder of RBSS, said: “The Russian airstrike and the regime were falsely stating that they were attacking the Daesh and destroying the locations of ISIS, when in actual fact they were harming the civilians.
"There are a lot of schools and hospitals that were bombed particularly in the east of Raqqa or Deir al Zor.
"The international (coalition) would be more targeted at a point, like on a car.
"The Russian strikes and regime is much more severe targeting many buildings and large areas.”
RBSS has 17 members inside Raqqa.
Four of their group have been killed by Daesh, two of them were assassinated last year in Turkey.
:: Watch a Sky News special programme Inside Syria: The Raqqa Resistance on Sky News today at 9.30am, 11.30am and 4.30pm.