Both government forces and supporters of the former Assad regime in Syria likely committed war crimes in March when around 1,400 people were killed, according to the UN commission's investigation.
Most of those killed were civilians, from the alawite minority group.
Rami Abdulrahman, head of the British-based Syrian Human Rights Observatory (SOHR) said in a statement in March that it was "one of the largest massacres in the Syrian conflict".
