The bloodshed comes a day after dozens more were killed in the opposition-held area and as the United Nations pleaded for a truce in the seven-year-old war to allow for aid deliveries and the evacuation of the ill and wounded.
Fresh regime strikes killed 15 civilians on Wednesday in an opposition-held enclave near Damascus where overwhelmed medics were still treating the survivors of the Syrian conflict's bloodiest day in months.
The district of Eastern Ghouta, controlled by the opposition and militias, suffered some of its worst bloodshed in years on Tuesday and the toll continued to mount overnight.
The bloodshed comes as the United Nations put out a statement pleading for a truce in the seven-year-old conflict to allow for aid deliveries and the evacuation of the ill and wounded.
TRT World's Denee Savoia reports.
"The civilian toll is now 80. Two wounded people died after midnight," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
"This was the highest civilian toll in Syria in nearly nine months, and one of the bloodiest days for Eastern Ghouta in several years," the head of the Britain-based monitoring group said.
At least 19 children and 20 women are among the dead, and around 200 were wounded.
There was no respite for Ghouta residents as regime warplanes returned on Wednesday morning and carried out strikes that killed 15 civilians and wounded dozens.
At least eight were killed in the town of Hammuriyeh, four in the town of Beit Sawa, and three in the main town of Douma, the Observatory said.
Civilians had been bracing for more raids as the regime appeared intent on ratcheting up the pressure on Eastern Ghouta, an opposition-held pocket on the capital's doorstep.
"Please break up all gatherings and clear the streets," blared an announcement from mosque minarets in Douma.
Surrounding areas and villages had been heavily battered by raids on Tuesday, flooding Douma's hospitals with wounded children.
Home to an estimated 400,000 people, the Eastern Ghouta region has been included in a de-escalation deal that was meant to bring calm to several zones across the country.
The UN said existing agreements on the delivery of aid were not being honoured and stressed that "if access was granted, three convoys could be dispatched each week, reaching over 700,000 people in [Idlib, Arin, Raqqa, Hasakah and Al Rukban camp] in two months."
Philip Owira has more.
Chemical weapon use
The latest casualties in Eastern Ghouta, on paper also a de-escalation zone, come as Washington threatened military action over the reported use of chemical weapons in the enclave, which the regime and its allies have besieged since 2013.
The US Department of State said on Monday it had recorded six suspected chemical attacks in Syria in the past 30 days.
France's Foreign Minister Jean-Yves Le Drian said on television on Wednesday there were indications Syrian regime forces were using toxic gas against civilians although the UN would need to confirm that.
Asked whether he wanted Turkish armed forces to withdraw from Syria, Le Drian replied that he wanted "the withdrawal of all of those who ought not to be in Syria, including Iranian militia, including Hezbollah."
While not specifically calling for Turkey to pull back from its offensive against YPG/PKK in northern Syria, he said that Ankara should not worsen the conflict.
Fighting also raged in the northwestern province of Idlib, where the UN said the violence "made a mockery" of the de-escalation zones agreed last year in a bid to pave the way for an end to the war.
Daily fighting is claiming a growing human toll and displacing thousands.
The UN commission said at least three hospitals were hit in recent strikes and shelling.
"These reports are extremely troubling, and make a mockery of the so-called 'de-escalation zones' intended to protect civilians from such bombardment," said Paulo Pinheiro, chair of the Commission.