The UN Commissioner for Human Rights has told Russia that air strikes on civilian targets in the Syrian city of Aleppo may amount to crimes against humanity which could be brought before the International Criminal Court (ICC).

Key points: UN Chief warns Russia on illegal use of incendiary weapons

UN Chief warns Russia on illegal use of incendiary weapons Death toll rises, no reply from Syria government on UN convoys

Death toll rises, no reply from Syria government on UN convoys Russia rejects the proposal saying it "oversteps"

High Commissioner Zeid Ra'ad al Hussein has compared the situation in Aleppo to the World War II battles of Warsaw and Stalingrad and said calling the enemy a "terrorist organisation" was not an excuse to ignore the laws of war.

Mr Zeid said Syria's Government and its allies attacked targets protected by international law, including medical units, aid workers and water-pumping stations.

The rebels' use of inaccurate, homemade mortars that fire gas cylinders packed with explosives and shrapnel, was also totally unacceptable, he said in a statement

"Such a referral would be more than justified given the rampant and deeply shocking impunity that has characterised the conflict and the magnitude of the crimes that have been committed, some of which may indeed amount to war crimes and crimes against humanity."

Commissioner Zeid said Syria's Government and its allies attacked targets protected by international law. ( Reuters/Denis Balibouse )

Mr Zeid said initiatives to resolve the situation in besieged, rebel-held eastern Aleppo should include proposals to limit the use of the veto by the permanent members of the UN Security Council.

This would enable major powers to refer the matter to the International Criminal Court, a step previously blocked by Russia and China.

Russia diplomatically dismissed the UN chief's proposal.

In New York, Russia's UN Ambassador Vitaly Churkin told reporters it was "not his responsibility to discuss veto powers".

"Unfortunately my good friend has been overstepping the limits of his responsibilities quite a bit and this is unfortunate."

The Russian Defence Ministry did not respond to a request for comment.

When asked how Russia viewed the suggestion of limiting the veto rights of permanent Security Council members, Kremlin spokesman Dmitry Peskov said: "Negatively".

Last week Peskov said the Russian air force would continue to support Syrian Government troops and that what he called the "war on terror" would continue.

Russia is the main military backer of Syria's President Bashar al-Assad.

Reuters