At least 15 civilians, including a child and three women, died on Sunday in shelling of towns east of Damascus, a monitoring group said, while tanks pounded rebel enclaves on the Syrian capital's edges.
The army said it had laid siege to rebels east of Damascus, although the Syrian Observatory for Human Rights said battles and shelling raged on in the area.
Elsewhere, loyalist troops made a rare advance in the north and took control of a strategic village near the city of Aleppo, said the monitoring group.
Fifteen people, among them a child and three women, were killed in shelling of the towns of Jisreen, Kafr Batna and nearby areas, said the Observatory, which relies on a network of activists, doctors and lawyers for its reports.
Another six rebel fighters were killed in fighting in Nashabiyeh, also east of Damascus, said the Britain-based group.
Some of Syria's fiercest and best organised rebel groups hold enclaves east of Damascus -- known as the Eastern Ghouta area -- and the army has for the past several months fought to halt the insurgents in their tracks.
In a statement carried by state news agency SANA, the military said on Sunday it has laid siege to rebels in Eastern Ghouta.
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"Units from our army in the Eastern Ghouta carried out a special operation yesterday, in collaboration with honest citizens from the region, that resulted in the tightening of a siege on the whole of the area," it said.
But Observatory director Rami Abdel Rahman told AFP that many villages and towns were still under rebel control.
On the edges of Damascus, meanwhile, army tanks pounded rebel enclaves in Qadam and Jobar, said the Observatory.
In the north, the army took control of the flashpoint village of Aziza, following several days of fierce bombardment, it said.
Rebel prime minister Ghassan Hitto, meanwhile, travelled to the Idlib region of northwest Syria on Sunday to pursue his consultations on forming an interim government, his opposition National Coalition announced on its Facebook page.
Sunday's violence came a day after at least 116 people were killed across Syria, said the Observatory.
The UN says more than 70,000 people have been killed in Syria since March 2011, when the army unleashed a brutal crackdown against dissent, morphing a peaceful revolt against the regime into an insurgency.