The investigation, conducted by an independent panel, found 256 children were killed by government forces, some of them tortured to death.
The report said government forces used excessive force to "shoot indiscriminately at unarmed protesters" while snipers targeted others in the upper body and head.
It found Syrian security forces cooperating with militias were given "shoot to kill" orders to crush demonstrations.
"These crimes include murder, torture, rape and other forms of sexual violence," said the panel's chairman, Paulo Sergio Pinheiro, a Brazilian professor. "We have a very solid body of evidence."
The commission said that it had interviewed 223 victims and witnesses including defectors from Syria's military and security forces since September.
The investigators were not permitted to enter Syria. Read More