Government forces carried out heavy bombardment Friday of a rebel-held district on the eastern edge of the Syrian capital in support of advancing troops, an activist and monitor said.
Ain Terma lies in Eastern Ghouta, the largest rebel enclave around Damascus, which is part of an envisioned "de-escalation zone" agreed by regional powers in May.
The neighbourhood links Eastern Ghouta to the opposition-held Damascus neighbourhood of Jobar.
"There were a number of air strikes and the regime is trying to storm Ain Terma," said Hamza Abbas, an activist inside the area.
"The houses are shaking from the intensity of the shelling and I can see smoke," he told AFP.
The Syrian Observatory for Human Rights, a Britain-based monitor of the war, said at least five regime air strikes and three regime rockets hit Ain Terma.
Government troops on the ground seized the neighbourhood's marble factory and surrounding territory, said Observatory head Rami Abdel Rahman.
"The government wants to capture Ain Terma to cut off Jobar from the rest of Eastern Ghouta," he told AFP.
Abdel Rahman said at least 11 regime fighters and 19 rebels had been killed in Ain Terma and Jobar since the army began escalating operations there on June 20.
Ain Terma is held by Faylaq al-Rahman, which is allied to former Al-Qaeda affiliate Fateh al-Sham Front.
Activists have accused Syria's government of using chlorine as part of the assault, a claim the army has fiercely denied.
According to the United Nations, regime troops used chlorine in attacks on three Syrian villages in 2014 and 2015
