(Adds detail from report)
By Stephanie Nebehay
GENEVA, Sept 11 (Reuters) - U.N. human rights investigators said on Wednesday Syrian government forces had massacred civilians, bombed hospitals and committed other war crimes in widespread attacks to recapture territory from rebels this year.
Opposition forces, including Islamist foreign fighters, have also perpetrated war crimes including executions, hostage-taking and shelling of civilian neighbourhoods, the investigators said in their latest report, covering the period of May 15-July 15.
"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," said the report by the U.N. commission of inquiry, which is led by Paulo Pinheiro of Brazil.
The independent experts said they had received allegations about the use of chemical weapons "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.
The team of some 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". (Reporting by Stephanie Nebehay, editing by Tom Miles and Mark Heinrich)