GENEVA (Reuters) - Syria’s air force deliberately bombed water sources in December, a war crime that cut off water for 5.5 million people in and around the capital Damascus, the U.N. Independent International Commission of Inquiry on Syria said on Tuesday.

A boy transports water on a bicycle in the rebel-held besieged Douma neighbourhood of Damascus, Syria. REUTERS/Bassam Khabieh

The commission said it had found no evidence of deliberate contamination of the water supply or demolition by armed groups, as the Syrian government maintained at the time.

Rebels had controlled the springs of the Wadi Barada valley, northwest of Damascus since 2012 and faced a major offensive by Syrian government forces and their allies, despite a ceasefire deal. The rebels withdrew at the end of January.

The commission, led by Brazilian investigator Paulo Pinheiro, said there were no reports of people suffering water contamination on or before Dec. 23, when the Syrian air force hit al-Fija spring with at least two air strikes.

“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 five 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.

Syrian ambassador Hussam Aala did not comment directly on the attack during a debate at the Human Rights Council in Geneva, but said his government rejected allegations that it had attacked civilians or civilian infrastructure.

The attack was one of several war crimes committed by forces loyal to Syrian President Bashar al-Assad, the report said.

SCHOOL COMPLEX

In another incident, it said a Sukhoi-22 jet dropped four bombs on a school complex in opposition-held territory in October. As aid workers arrived, a second Sukhoi dropped four more. In all, 21 children and 15 adults died and 114 others were wounded.

Syria’s ally Russia denied the attack took place, the report said, but evidence from witnesses, photos, satellite imagery and bomb fragments confirmed Syrian government involvement.

“There are reasonable grounds to believe that the Syrian Air Force deliberately targeted the Haas schools complex,” it said.

On Feb. 1, aircraft - most likely Syrian or Russian - bombed the longstanding and well-marked headquarters of the Syrian Arab Red Crescent in the town of Idlib, the report said.

And in a series of war crimes, patterns of attacks also strongly suggested that pro-government forces systematically targeted medical facilities, said the report, which covered the period between July 21, 2016, and Feb. 28 this year.

Its publication came less than two weeks after the commission said that Syrian government aircraft deliberately bombed and strafed a humanitarian convoy, killing 14 aid workers, in September last year.

The commission also documented the use of lethal chlorine gas on multiple occasions by government and pro-government forces, in the suburbs of Damascus and in Idlib province.

There was no evidence of Russian involvement in chlorine attacks, the report said.

It also cataloged atrocities by Islamic State and the group formerly known as the Nusra Front, the two combatants designated as terrorists by the U.N. Other rebel groups were also blamed for displacing communities during their offensives.

(The story was refiled to correct the sixth paragraph to add Syrian ambassador’s comment and make clear he did attend the debate)