GENEVA(Reuters) - Both sides in the battle for Aleppo committed war crimes, including Syrian government aircraft that "deliberately" bombed and strafed a humanitarian convoy, killing 14 aid workers and halting relief operations, U.N. investigators said on Wednesday.
Syrian and Russian forces conducted "daily air strikes" on rebel-held eastern Aleppo between July and its fall on December 22, killing hundreds and destroying hospitals, they said in their latest report.
Cluster munitions were "pervasively used" and air-dropped into densely-populated areas, it said, amounting to the war crime of indiscriminate attacks.
But investigators could not say whether both Syrian and Russian forces had used them in Aleppo or only one had. They also did not attribute any specific war crime investigated to Russian forces.
"Throughout the period under review, the skies over Aleppo city and its environs were jointly controlled by Syrian and Russian air forces ... (They) use predominantly the same aircraft and weapons, thus rendering attribution impossible in many cases," the report said.
The U.N. Commission of Inquiry's report - released as Syrian peace talks continue in Geneva - covers the July-December period and is based on 291 interviews with victims and witnesses, as well as analysis of forensic evidence and satellite imagery.
Syrian helicopters unleashed toxic chlorine bombs "throughout 2016" on Aleppo, a banned weapon that caused hundreds of civilian casualties there, the report said.
At least 5,000 pro-government forces also encircled eastern Aleppo in a "surrender or starve" tactic, it said.
Opposition groups shelled government-controlled western Aleppo, killing and injuring dozens, the report said. They prevented civilians from fleeing eastern Aleppo, using them as "human shields", and attacked the residential Kurdish district of Sheikh Maqsoud, both war crimes.
The U.S.-led coalition did not conduct any offensive air missions over Aleppo in the second half of the year, they said.
"Dumb bombs"
Syrian and Russian warplanes dropped unguided munitions, known as indiscriminate "dumb bombs" rather than smart bombs that have electronic sensors to find their targets, the report said.
These included aerial bombs, air-to-surface rockets, cluster munitions, incendiary bombs, barrel bombs, and weapons delivering toxic industrial chemicals.
The investigators accused the Syrian government of a "meticulously planned and ruthlessly carried out" air strike on a U.N. and Syrian Red Crescent convoy at Orum al-Kubra, in rural western Aleppo on Sept 19 that killed 14 aid workers.
A previous U.N. inquiry had been unable to determine who conducted the strike.
"By using air-delivered munitions with the knowledge that humanitarian workers were operating in the location, Syrian forces committed the war crimes of deliberately attacking humanitarian relief personnel, denial of humanitarian aid, and attacking civilians," the report said.
Survivors "consistently described" three stages of attack.
"First helicopters dropped barrel bombs, which struck the warehouse and a family home nearby ... Subsequently, planes, described by several witnesses as Sukhoi jets, carried out attacks, killing several aid workers. Lastly the aircraft fired machine guns at survivors."
During the recapture of eastern Aleppo, pro-government forces arrested doctors and aid workers and committed reprisal executions, the report said.
(Reporting by Stephanie Nebehay; Editing by Gareth Jones)
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