United Nations High Commissioner for Human Rights Zeid Ra'ad Al Hussein arrives for a media briefing at the U.N. European headquarters in Geneva, Switzerland October 12, 2016. REUTERS/Denis Balibouse

GENEVA (Reuters) - Syria’s government forces and their allies have almost certainly violated international law and probably committed war crimes by the latest bombardment of civilians hoping to be evacuated from eastern Aleppo, the U.N. human rights chief said on Wednesday.

“The Syrian Government has a clear responsibility to ensure its people are safe, and is palpably failing to take this opportunity to do so,” U.N. High Commissioner for Human Rights Zeid Ra’ad al Hussein said in a statement.

“The Government of Syria is also obliged under international law to provide medical assistance to all sick and wounded people – civilians and fighters alike,” he said.

He added that he was appalled that a deal to evacuate many thousands of civilians from eastern Aleppo appeared to have collapsed, and said it was outrageously cruel that hope of survival had been snatched away from them.

A evacuation of besieged rebel districts was announced late on Tuesday but did not go ahead as planned early on Wednesday after Iran, one of President Bashar al-Assad’s main backers, imposed new conditions, saying it wanted the rebels to allow the simultaneous evacuation of two Shi’ite villages.

A ceasefire that had coincided with news of the evacuation plan broke down and fighting raged again in Aleppo on Wednesday.

“While the reasons for the breakdown in the ceasefire are disputed, the resumption of extremely heavy bombardment by the Syrian Government forces and their allies on an area packed with civilians is almost certainly a violation of international law and most likely constitutes war crimes,” Zeid said.

“The agreement was there, the buses were in place, the first convoy had set off and was then reportedly blocked by pro-Government militia. This is inexcusable.”