Syrian rescue workers rush to help wounded people after air raids on the rebel-held Eastern Ghouta.
At least 23 civilians are reported to have been killed in a new wave of Syrian government air strikes on a besieged rebel enclave near Damascus.
Rescuers and a monitoring group said warplanes bombed several towns in the Eastern Ghouta on Wednesday, causing buildings to collapse on residents.
More than 130 people are now said to have died since the government intensified its bombardment on Monday.
The UN has said the situation there is "extreme" and appealed for a ceasefire.
An estimated 400,000 people are trapped in the Eastern Ghouta, which has been under a siege by pro-government forces since 2013.
There are severe shortages of food, fuel and medicines, and more than 600 critically sick and wounded patients urgently need to be evacuated for treatment.
Tuesday was one of the deadliest days in the Eastern Ghouta for months, with government air and artillery strikes on 10 towns across the area. Eighty people, including 21 children, were killed.
The bombardment resumed on Wednesday morning. Ten people were killed in the town of Beit Sawa, according to the Syria Civil Defence, whose rescue workers are known as the White Helmets. Another eight died in Hamouriya and five in Douma.
A young man in Hamouriya told AFP news agency that his brother was among five children killed when a street where they had been collecting water was hit.
The Syrian Observatory for Human Rights, a UK-based monitoring group, put Wednesday's death toll at 34.
It reported that a total of 401 people, including 103 children and 69 women, had now died since the government stepped up its assault on 29 December.
Many people living in nearby government-controlled districts of Damascus have also been killed by shells fired by rebels based in the Eastern Ghouta.
With a government offensive under way in the rebel-held north-western province of Idlib, and Turkish-backed rebel forces attacking the neighbouring Kurdish enclave of Afrin, the UN's regional humanitarian co-ordinator for the Syria crisis warned on Tuesday that there were "multiple fronts were people are under extreme danger".
"We feel we've reached a breaking point," Panos Moumtzis told reporters in Beirut.
He also said it was "really outrageous" that the government had not authorised a single aid delivery to the Eastern Ghouta and other besieged areas in two months.
Eastern Ghouta is the "epicentre of suffering" in Syria
"Humanitarian diplomacy is failing," he said. "We are not able to reach the conscience or the ears of politicians, of decision makers, of people in power."
Mr. Moumtzis and other UN officials have called for an immediate cessation of hostilities, lasting for at least one month throughout Syria, to enable the delivery of humanitarian aid and services, plus evacuation of the critically ill.