Bombardments on opposition-held towns have killed at least 44 people and wounded more than 100, Syrian activists say.
The Syrian government has launched dozens of air strikes on several rebel-held areas around Damascus, killing at least 76 people after the fighters shelled the capital in a rare move, activists say.
The Syrian Observatory for Human Rights, a UK-based monitoring group, said on Thursday that at least six children were among those killed in the bombings on the suburbs of Damascus.
At least 140 people were injured in nearly 60 air raids on Eastern Ghouta, districts of Douma – a bastion of the armed group Jaish al-Islam – as well as Kaferbatna, Irbin, Saqba and Ain Tarma.
In Douma, the government air strikes brought chaos, with an AFP photographer reporting civilians streaming into a makeshift clinic.
Medics, overwhelmed by the number of arrivals, were forced to treat some on the floor.
Eastern Ghouta is a key rebel bastion on the outskirts of Damascus, and has been under siege for nearly two years.
The SOHR said that security forces also fired surface-to-surface missiles in the area.
The wave of air raids came after dozens of mortar shells, artillery, and missiles targeting Damascus were fired by Jaish al-Islam starting early on Thursday morning.
Activists said that five people were killed and dozens injured by the armed group’s shelling. Syrian state news agency SANA reported that three people had been killed.
Shells launched by rebels landed in Old Damascus, Mazra’a, Muhajreen, Barzeh, Mezzeh, Baramkeh and other districts in the government-controlled city.
Mid-term exams at Damascus University were postponed, according to residents, due to the heavy shelling, which struck the buildings of the economics and law departments.
Jaish al-Islam leader Zahran Aloush has declared Damascus a military zone and announced a curfew for a second time.
Aloush said his group was targeting military and government positions, but activists said most shells landed in residential areas.
He also said on Twitter that the attacks were in response to government massacres in the eastern Damascus countryside.