The UN Commissioner for Human Rights, Zeid Ra'ad al Hussein, did not mention Russia by name and said all sides in the conflict had violated international law.
The United Nations’ human rights chief has described Aleppo as a “slaughterhouse”, saying the siege and bombing of eastern districts constitute “crimes of historic proportions”.
Zeid Ra’ad al Hussein, the UN High Commissioner for Human Rights, did not specifically mention Russia whose planes have backed the Syrian air force in bombarding the rebel-held part of the city.
In a video speech to the UN Human Rights Council in Geneva he accused all parties of violating international law.
“Armed opposition groups continue to fire mortars and other projectile into civilian neighbourhoods of western Aleppo, but indiscriminate air strikes across the eastern part of the city by Government forces and their allies are responsible for the overwhelming majority of civilian casualties, and these violations constitute war crimes,” Zeid said.
He called for major powers to put aside their differences and refer the situation in Syria to the prosecutor of the International Criminal court (ICC).
The special one-day session was requested by Britain and its allies including the United States. The Council voted to set up a special independent inquiry into events in Aleppo.
Russia has denied deliberately targeting civilians, arguing it is fighting terrorists. Britain rejected that argument at the session: the UK’s minister for Africa and the Middle East, Tobias Ellwood, said the Assad government and Russia were using “the pretence of tackling terrorism” in Syria to kill hundreds of thousands of civilians, including children.
Describing Russia’s action as “shameful” for a permanent member of the UN Security Council, he said it was driving radicalisation, and fuelling terrorism rather than tackling it.
The Russian ambassador accused Britain and its allies of trying to save terrorists from being targeted.
Moscow has announced an extension of its ceasefire until Saturday evening. It says the pause is to allow civilians and fighters who lay down their weapons to leave Aleppo.
The Foreign Minister Sergei Lavrov told a briefing in the Russian capital that he suspected the West wanted to protect a Syrian militant group.
“Jabhat al-Nusra, Ahrar al-Sham and other organisations that cooperate with them are sabotaging the UN efforts, that were made with the support of Russia and Syrian government, to set up humanitarian supplies in the east of Aleppo. The routes that such humanitarian aid can go through are being directly shelled,” he said.
Russia was recently accused by the US of pursuing a “Grozny strategy” in Aleppo – “to simply bomb indiscriminately and terrorise every human being” in the words of the US Secretary of State John Kerry.
The UN said medical evacuations from eastern Aleppo had not begun as hoped on Friday because a lack of security guarantees and agreement with all sides prevented aid workers from operating.
It wants to use a pause in the bombing announced by Russia to evacuate hundreds of sick and wounded people and to make food and aid deliveries, UN humanitarian spokesman Jens Laerke said.
Many people in eastern Aleppo are understood to be reluctant to leave.