Pro-government forces carried air raids in Syria's eastern Ghouta rebel-held enclave overnight on Monday and early on Tuesday after the heaviest one-day death toll from bombardment there in three years, a war monitor said.
More than 100 people were killed in air raids, rocket strikes and shelling of the area near Damascus on Monday, said the Britain-based Syrian Observatory for Human Rights.
The United Nations called for an immediate ceasefire in the area on Monday, saying the situation was "spiralling out of control" after an "extreme escalation in hostilities."
The violence in eastern Ghouta is part of a wider escalation in warfare on several fronts in Syria in recent months as President Bashar Assad pushes to end the seven-year rebellion against him.
Assad's most powerful ally, Russia, has been pushing a diplomatic track at the same time as the increase in fighting, resulting in the establishment of several "de-escalation zones."
Eastern Ghouta is in one of these areas, where violence is meant to be contained, but the agreement does not include a former al-Qaida affiliate which has a small presence there.
Other insurgent groups in eastern Ghouta, including Islamist factions, say the Syrian government and Russia are using the jihadist presence as a pretext to continue their bombardment.
Neither the Syrian military nor Russia commented on the renewed bombardment in eastern Ghouta, but they have often said they do not target civilians.
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The Observatory said the intensified bombing was in preparation for a pro-government ground offensive against the enclave and that a rebel group there had foiled an attempt by Syria's army to advance at al-Marj overnight.