UN human rights investigators have in their latest report on the Syria conflict accused both sides of committing war crimes.
The report accused Syrian government troops of massacaring civilians, bombing hospitals and committing other war crimes in their bid to recapture territory from rebel hands in recent months.
The perpetrators of these violations and crimes, on all sides, act in defiance of international law. They do not fear accountability.
Opposition forces, including foreign fighters, have committed war crimes including executions, hostage-taking and shelling civilian neighbourhoods, the report added.
Evidence confirms at least eight massacres have been carried out by President Bashar Assad's government and supporters and one by rebels over the past year and a half
"The perpetrators of these violations and crimes, on all sides, act in defiance of international law. They do not fear accountability. Referral to justice is imperative, " the UN commission of inquiry, led by Brazilian Paulo Pinheiro, said.
The four-member commission also said it was probing nine more suspected mass killings since March. With those, it said, the illegal killing was confirmed but the perpetrator could not yet be identified. In other cases, it said, the circumstances of the killing were not sufficiently clear to be able to determine the legality.
On chemical weapons, the independent experts said they had received allegations about their use "predominantly by government forces."
"On the evidence currently available, it was not possible to reach a finding about the chemical agents used, their delivery systems or the perpetrators. Investigations are ongoing," the report said.
A team of 20 investigators carried out 258 interviews with refugees, defectors and others, in the region and in Geneva, including via Skype, for their 11th report in two years. They have never been allowed into Syria despite repeated requests.
The report called for a political solution to Syria's civil war and urged other states to "stop weapons transfers in view of the clear risk that they will be used to commit serious violations of international law".