The report, released Sunday by the London-based Oxford Research Group, says 11,420 children aged 17 and under were killed between the start of the conflict in March 2011 and August 2013.
Summary executions and torture have been used against children as young as one, according to the report, entitled Stolen Futures: The Hidden Toll of Child Casualties in Syria.
The report's findings include:
- 26.5 per cent of children died from bullets, including those summarily executed and targeted by snipers.
- 764 children were summarily executed.
- 389 were killed by sniper fire.
- more than 100 children were tortured.
- children in older age groups were targeted more often than younger children, and overall boys outnumbered girls killed by about 2 to 1.
- the highest child casualty figures were in the governorate of Aleppo, but relative to its size, the worst-affected governorate was Daraa.
Overall, 113,735 civilians and combatants were killed in the 30-month period studied by the independent think-tank.
"What is most disturbing about the findings of this report is not only the sheer numbers of children killed in this conflict, but the way they are being killed," the report's co-author Hana Salama said.
The Oxford Research Group said the majority of children were killed during bombings in their neighbourhoods.
The UK-based group is calling for fighters from all sides to undergo training in saving civilians' lives.