GENEVA - U.N. investigators are calling for perpetrators of crimes against civilians in Syria’s long-running civil war to be prosecuted and brought to justice. The latest report submitted to the U.N. Human Rights Council in Geneva by the International Commission of Inquiry on Syria documents multiple atrocities and gross violations committed by all warring parties.

The Commission of Inquiry has run out of patience with U.N. member states it accuses of having done little to hold perpetrators of crimes in Syria accountable. Commission Chair Sergio Pinheiro calls the deadlock at the Security Council on Syria after six years of war "reprehensible" and at times bewildering.

He told delegates at the U.N. Human Rights Council that civilians continue to be deliberately attacked, deprived of humanitarian aid, forcibly displaced and arbitrarily detained or held hostage by all warring parties.

He said most civilians are killed and maimed by the unlawful use of conventional arms, particularly through indiscriminate shooting and aerial bombardments in populated areas.

“We have a duty under our mandate, however, to document the unambiguously illegal use of prohibited chemical weapons, in blatant violation of international law and attribute responsibility accordingly," he said. "In several instances, Government forces used chemical weapons against civilians in opposition-held areas, including in Khan Shaykhun, Idlib on 4 April.”

Pinheiro says that chemical attack killed 80 people, mostly women and children, injuring hundreds more. He says the attack took place during a Syrian and Russian aerial campaign in northern Hama and southern Idlib that targeted medical facilities.

These charges elicited a hostile and angry reply from Syrian Ambassador Hussam Edin Aala, who accused the Commissioners of using fabricated, biased information from unreliable sources. He called the assertion his Government used chemical weapons a pack of lies.