March 14 (UPI) -- Syria's air force committed a war crime by deliberately bombing the water supply outside Damascus last December that affected 5.5 million people, U.N. investigators said Tuesday.
The Syrian government previously blamed rebels for damaging the Ain al-Fijeh spring in the battle for the Wadi Barada valley.
The U.N. Independent International Commission of Inquiry on Syria said in its report two airstrikes caused the damage on Dec. 23. Government forces' offensive attempted to regain control of Wadi Barada in the hills northwest of Damascus.
The Damascus Water Authority announced on that date that it had cut off water supplies, accusing armed groups of contaminating the water with fuel.
The bombing was among several violations documented by the U.N. investigators.
"Vicious attacks on civilian infrastructure, including hospitals, schools and water sources have resulted in astounding numbers of civilian casualties and the massive destruction of buildings meant to provide essential services to the population," the report said. "The deliberate targeting of medical facilities and workers by pro-government forces, amounting to war crimes, has led to a severe weakening of healthcare infrastructure, which after almost six years of conflict is already depleted to impossibly low levels. Prevented from accessing life-saving treatments, civilians are the main casualties of this practice."
The U.N. report based its conclusions on interviews with residents, satellite imagery and publicly available information.
The said it had found no evidence of deliberate contamination of the water supply by rebels.
"While the presence of armed group fighters at [the] spring constituted a military target, the extensive damage inflicted to the spring had a devastating impact on more than 5 million civilians in both government and opposition controlled areas who were deprived of regular access to potable water for over one month," the commission's report said.
"The attack amounts to the war crime of attacking objects indispensable for the survival of the civilian population, and further violated the principle of proportionality in attacks," the report added.
The report also found another war crime when the Syrian air force bombed a complex of five schools in Haas, a village in rebel-held Idlib province, on Oct. 26, killing 21 children among 36 civilians who died. It described it as a "ruthless airstrike."
The report said video footage taken by an interviewee shows a Sukhoi 22 jet dropping a parachute bomb and remnants of it in the area.
Russia, which has carried out airstrikes to support the government, claimed the pictures of the incident were fabricated. But the U.N. investigators said their evidence disputes the Russians' view.
The commission also described the use of lethal chlorine gas by government and pro-government forces in the suburbs of Damascus and Idlib province.
"The use of chlorine, which causes superfluous injury and unnecessary suffering, is inherently indiscriminate because its effects cannot be limited in time and space," the report said.
The report was published a day before the sixth anniversary when the uprising started against President Bashar al-Assad. The civil war has left more than 470,000 people dead and injured 1.9 million, the Syrian Center for Policy Research said.
Two weeks ago, the commission said that both sides in last year's battle for Syria's Aleppo city committed war crimes.