The UN commission investigating atrocities in Syria has placed much of the blame on President Bashar al-Assad, saying that the Syrian regime was responsible for the majority of civilian deaths.
The head of the UN commission, Paulo Sergio Pinheiro said Islamic State and other militants are not "the sole agents of death and destruction inside Syria."
“The Syrian government remains responsible for the majority of the civilian casualties, killing and maiming scores of civilians daily, both from a distance using shelling and aerial bombardment and up close, at its checkpoints and in its interrogation rooms,” Pinheiro told the UN Human Rights Council in Geneva.
"Checkpoints are often the starting point of a horrific journey of disappearance, torture, sexual abuse and, for many, death. Checkpoints are used to enforce sieges and to trap civilians in areas under indiscriminate bombardment."
The report by the commission also details crimes committed by Islamic State, including massacres, executions of minors and amputations.
Pinheiro criticised the inaction by the international community in relation to the conflict, which has killed an estimated 190,000 people.
"We have charted the descent of the conflict into the madness where it now resides. ... But we have been faced with inaction," he said.