The Syrian Observatory for Human Rights war monitor said raids had resumed a day after more than 40 people were killed in other strikes on Douma, where dozens also suffered from breathing difficulties.

Negotiators in Douma and the Syrian state news agency SANA said a deal had been reached for negotiations with the Jaish al-Islam rebel group, who hold Douma, the last pocket of resistance in Ghouta.

On Sunday morning, a civilian committee taking part in the talks between the rebels and Russia announced "a ceasefire and the resumption of talks today" hoping it will lead to a "final accord".

SANA, citing an official source, said the "Jaish al-Islam terrorists are requesting negotiations with the Syrian government and the government will begin these negotiations within two hours".

The Britain-based Observatory said "regime aircraft have resumed bombardment of Douma" after a brief lull overnight, adding that the strikes were aimed at piling pressure on Jaish al-Islam.

It added, however, that "despite the renewed strikes, negotiations are underway".

According to the Observatory, air raids killed 42 people in Douma on Saturday and 30 of Friday.

It also reported that 70 civilians suffered from breathing difficulties on Saturday, and that 11 of them, including four children, had died.

The White Helmets rescue organisation, Jaish al-Islam and Syria's main opposition forces however claimed that Douma had been hit by a chemical attack.

Syrian state media denounced the allegations as "fabrications".

The Observatory's Abdel Rahman said he could not "confirm or deny" the claims of a chemical attack.

But he said the civilians had difficulty breathing probably because of the amount of smoke that rose over Douma "after the air strikes".

A regime offensive against Ghouta since February 18 has killed more than 1,600 civilians and sliced the area into three isolated pockets, each held by different rebel factions.

The first two were evacuated under Russian-brokered deals last month that saw more than 46,000 rebels and civilians bussed to opposition-held Idlib province in the northwest.

But talks with Jaish al-Islam which controls Douma -- the third and last pocket -- have faltered despite a preliminary accord last week that saw nearly 3,000 fighters and civilians bussed to northern Syria.