The Syrian Observatory for Human Rights said airstrikes pounded opposition-held suburbs east of Damascus on Tuesday, killing at least 35 people.

The Britain-based war monitor said Assad regime aircraft and shelling hit the towns of Harasta, Hamouriya, Douma and other parts of the eastern Ghouta pocket near the capital.

Several children were among Monday's dead.

On Wednesday, airstrikes killed another 23 civilians, including five children, the Syrian Observatory for Human Rights said.

The latest bloodshed came a day after strikes and shelling killed at least 31 civilians in the area, which has been besieged by regime forces since 2013.

The raids also came after a heated exchange between the United States and Russia at the United Nations over the reported use of chemical weapons by Bashar al-Assad's regime.

Regime or allied forces have fired suspected chlorine-filled munitions on targets in Eastern Ghouta on several occasions in recent weeks, sparking U.S. warnings of military action.

Russia, Assad's main backer, retorted that "no perpetrators have been identified" and accused the United States of orchestrating a "propaganda campaign" against the Syrian government.