The United Nations Security Council adopted a resolution on Saturday demanding a 30-day truce in Syria to allow aid deliveries and medical evacuations with the support of Assad ally Russia after a flurry of last-minute negotiations.
The vote comes as warplanes pounded eastern Ghouta, the last opposition enclave near Syria's capital, for a seventh straight day. U.N. Secretary-General Antonio Guterres appealed on Wednesday for an immediate end to "war activities" there.
Guterres, who has described Eastern Ghouta as "hell on earth," is to report to the council in 15 days on the ceasefire, diplomats said.
To win Russia's approval, language specifying that the ceasefire would start 72 hours after the adoption of the draft was scrapped, replaced by "without delay," and the term "immediate" was also dropped in reference to the aid deliveries and evacuations.
The Syrian Observatory for Human Rights said warplanes struck eastern Ghouta on Saturday evening, minutes after the U.N. Security Council adopted a resolution demanding a 30-day ceasefire in Syria.
The jets hit the town of Shifouniyeh in the opposition enclave, said the Britain-based monitoring group and two residents of the besieged suburbs near Damascus.
New air strikes on eastern Ghouta on Saturday took the civilian death toll from seven days of devastating bombardment to more than 500. A total of 127 children figure among the 513 dead in the bombing campaign that the regime launched last Sunday on the enclave just outside Damascus, the Syrian Observatory for Human Rights said.
The Britain-based monitor of the war said at least 35 civilians were killed in Saturday's strikes, including eight children. A night of heavy bombardment sparked fires in residential districts, it said.
Russia has vetoed 11 draft resolutions throughout the Syrian conflict to block action that targeted its ally. In November, it used its veto to end a UN-led investigation of chemical weapons attacks in Syria.
German Chancellor Angela Merkel and French President Emmanuel Macron wrote to Russian counterpart Vladimir Putin on Friday to ask him to back the ceasefire.
A previous draft had said the ceasefire would go into force 72 hours after the adoption, but that was dropped from the text in a bid to reach compromise with Russia.