The head of the United Nations human rights office said today that he considers the bombing of Aleppo, Syria, to constitute crimes “of historic proportions.”

Zeid Ra'ad Al Hussein, the UN’s High Commissioner for Human Rights, added his voice to a chorus of world leaders who have said that the Syrian and Russian bombardment of the city over the past few weeks constituted war crimes.

"The violations and abuses suffered by people across the country, including the siege and bombardment of eastern Aleppo, are simply not tragedies; they also constitute crimes of historic proportions," Zeid said in a video speech to the UN Human Rights Council in Geneva, Switzerland.

Read More: Russia Temporarily Stops Bombing Aleppo to Allow Civilian Aid

Zeid did not name Russia specifically, but said that “indiscriminate air strikes” were responsible for most of the civilian casualties, Reuters pointed out.

He said that if the violations were “knowingly committed” as part of a coordinated attack against civilians, they constitute “war crimes” and “crimes against humanity.”

Over the past month, bombing of Aleppo has killed nearly 500 people and injured 2,000 more, according to the BBC.

"The ancient city of Aleppo, a place of millennial civility and beauty, is today a slaughterhouse - a gruesome locus of pain and fear, where the lifeless bodies of small children are trapped under streets of rubble and pregnant women deliberately bombed," he said.

Russia has denied targeting civilians, however.

In Brussels, the President of the European Council, Donald Tusk, said that the council would consider all possible options to end the bombing in Syria if Russia and Syria do not stop, according to CNN.

Read More: Stunning Drone Footage Show Massive Destruction of Aleppo

"The EU is calling for an end to the atrocities and an immediate cessation of hostilities. It will consider all available options if these atrocities continue,” he said.

Earlier this month, a French official said that the Aleppo bombing should be investigated and prosecuted by the International Criminal Court. 

The Syrian army and Russian warplanes have been bombarding Aleppo for weeks, though earlier this week Russia announced a temporary ceasefire to allow injured civilians to leave the city.

The ceasefire was also supposed to allow UN humanitarian aid into the city to get to civilians, but the UN announced today that it would not begin medical evaluations as planned today because they were not assured safe passage.

Read More: Pope Francis Is Practically Begging for a Ceasefire So Syrian Children Can Escape

Last month a temporary humanitarian ceasefire ended shortly after a humanitarian convoy was attacked. Thirty trucks from the Syrian Red Crescent were carrying food and medicine to civilians in Aleppo when they were attacked, killing at least 20 people. The US blamed Russia for the airstrike on the convoy.

"We cannot begin safe, secure and voluntary evacuation of the sick and critically wounded and families," said Jens Laerke, UN deputy spokesman for humanitarian affairs.

Laerke said the UN still hopes to complete the humanitarian mission during the current truce.

The ceasefire is expected to last only through the weekend. Beyond that, there is still no clear ending to the ongoing conflict in Aleppo or Syria.