At least 50 people were killed Monday, a monitor said, as the UN said dozens of trucks carrying aid reached the main town of Douma.
The regime blocked some supplies as the first aid convoy arrived since the start two weeks ago of a bloody Russian-backed assault that has sparked outrage but little action from the West.
The 46 aid trucks arrived after fresh airstrikes hit besieged Eastern Ghouta and regime troops were reported to have retaken a third of the enclave in a rapidly advancing offensive.
An AFP reporter in Douma said warplanes were flying overhead and explosions from further bombardment on the enclave could be heard even as the aid was being unloaded.
According to the Observatory, an airstrike hit the Douma area about 1 km from where the trucks were unloading.
More than two weeks of airstrikes, artillery and rocket fire on the last major opposition-held enclave near Damascus have left hundreds dead and three quarters of the region’s housing damaged.
More bombs, including crude, improvised “barrel bombs,” were dropped in overnight raids on Monday, according to the Syrian Observatory for Human Rights.
At least 19 people were killed in the devastated town of Hammuriyeh, said the Britain-based monitoring group, which relies on a network of sources inside Syria.
Another 31 died elsewhere in the enclave, it added, bringing to 740 the number of civilians killed since the assault began, including at least 170 children.
The UN Human Rights Council on Monday ordered investigators to examine the latest violence.
The resolution, tabled by Britain, specifically condemned “the indiscriminate use of heavy weapons and aerial bombardments against civilians, and the alleged use of chemical weapons in Eastern Ghouta.”
Regime troops and allied forces have pushed into the enclave from the east in recent days, and by early Monday they had retaken a third of Eastern Ghouta, according to the Observatory.
“Regime forces are advancing at a high pace because operations so far are mostly conducted in farmland,” Observatory head Rami Abdel Rahman said, adding that they had advanced to within 2 km southeast of Douma.
The armed groups there, one of which is made up of fighters from Al-Qaeda’s ex-affiliate, have been lobbing mortar rounds and firing rockets on adjacent neighborhoods of Damascus, killing around 20 civilians in two weeks.
The latest ground offensive sent hundreds of civilians fleeing from their homes to other areas farther from the moving front line, compounding a humanitarian crisis which has drawn comparisons with the regime’s devastating 2016 assault to retake second city Aleppo.
A suffocating, years-long government siege has forced Eastern Ghouta’s estimated 400,000 inhabitants to scrape by on smuggled goods, produce from local farms and rare aid deliveries.
Monday’s convoy was delivering “health and nutrition supplies, along with food for 27,500 people in need,” the UN’s humanitarian coordination office OCHA said.
But an OCHA spokesperson said “the UN and partners were informed that many of the planned health supplies intended for Douma were not allowed to be loaded and not permitted to be replaced with other life-saving items.”
“The items included trauma kits and other life-saving supplies,” Linda Tom told AFP, calling for a solution to the problem ahead of the next delivery, slated for Thursday.
The International Committee of the Red Cross (ICRC), a partner in the aid convoy with the UN and the Syrian Arab Red Crescent, also pleaded for increased access.
“Repeated and continuous humanitarian access is essential and more must be granted in the coming period,” the ICRC’s Middle East director Robert Mardini said in a statement.
The US on Sunday condemned the assault and accused Moscow of ignoring a UN resolution calling for a 30-day cessation of hostilities.