Shelling and artillery fire continued in the rebel-held enclave of Eastern Ghouta during a supposed ‘five-hour ceasefire’ for its second consecutive day.
As a result, no civilians were able to exit the region and no humanitarian aid has yet gone in.
Russian President Vladimir Putin ordered the “humanitarian pause” but has blamed rebels for preventing civilians from leaving the area and suggested Russia would not “endlessly tolerate” the situation there.
"Shells keep regularly coming from there, there are 50-80 rocket and mortar strikes on some days.
"As we know well here in Russia, mortar rounds even hit the territory of the Russian Embassy and the trade mission.
"Shall we endlessly tolerate that? No, of course not."
Residents said they do not trust the truce, while the UN and aid agencies criticised the unilateral arrangement, saying it gives no guarantees of safety for people wishing to leave.
The limited pause came after a UN Security Council resolution that called for a nationwide 30-day ceasefire that failed to take hold.
While the relentless bombing has somewhat subsided in the region, which is home to around 400,000 civilians, the Syrian government's push to squeeze the insurgents out of the region continued.
On Wednesday, the European Union demanded that Russia, Iran and Turkey take responsibility for ensuring that the fighting stops in Syria and that a real 30-day halt in fighting is respected.
Opposition activists said the five-hour pause in eastern Ghouta was preceded by a barrage of airstrikes in the towns of Harasta and Douma, where Syrian troops and allied militia trying to push ahead with a ground offensive on a number of fronts from the east and west clashed with local insurgent groups.
The United Nations and aid workers had previously criticised the unilateral arrangement, saying the situation did now allow for convoys to go in or for people in need of medical evacuation to be brought out.
On the first day of the pause, activists reported around 20 civilians were killed, including several pulled from under the rubble from previous bombings.
Rami Aburrahman of the Syrian Observatory for Human Rights said that little violence was reported on Tuesday in the enclave just east of Damascus.
Mr Aburrahman said only a few artillery shells hit Douma, one of its suburbs.
Civilians caught in the violence have mocked Russian President Vladimir Putin's order for a five-hour open corridor.
Mr Putin said many militants in eastern Ghouta belong to groups listed by the UN as terrorist organisations.
He noted that the militants have regularly shelled Damascus, and many rounds landed near the Russian Embassy.
Ingy Sedky of the international Red Cross said for a humanitarian corridor to work, it needed to be well planned and implemented with the consent of all parties in the conflict.
The enclave's residents fear they could face harassment and possibly arrest if they go into government areas.
It has been under intense attack by the Syrian government, and more than 500 people have been killed since last week.