Beirut: Rebels fired dozens of rockets and mortar rounds Sunday at central Damascus, a monitoring group said, making good on a threat of retaliation for deadly air raids by the Syrian regime.

“Rebels launched more than 38 locally-made rockets and mortar rounds at several areas of central Damascus, including Al Maliki and Mazzeh neighbourhoods, as well as Arnus and Sabaa Bahrat squares,” the Syrian Observatory for Human Rights said.

“Several people were injured,” the Britain-based group said, without giving a precise casualty toll.

AFP journalists in Sabaa Bahrat square could hear the blasts, while ambulances and fire trucks rushed to the area.

State news agency SANA said the army fired back at the source, blaming rebels in the Eastern Ghouta area, without giving any initial report of casualties or naming the residential areas hit.

The attack comes two days after Zahran Alloush, head of the rebel Jaysh Al Islam (Army of Islam), warned on Twitter that his forces would launch a “rocket campaign against the capital” from Sunday.

“The rockets’ brigade is preparing for a rocket campaign against the capital, which will see rockets rain down every day... in retaliation for the regime’s savage air raids... against our people in the... Eastern Ghouta area,” Alloush wrote.

Government aircraft on Friday carried out a string of deadly raids against rebel-held Hammuriyeh in the besieged Eastern Ghouta area, located east of Damascus.

The Observatory said 56 people were killed, among them six children. Only five of the dead were fighters, said the group close to the Syrian opposition that relies on a network of activists and medics on the ground.

Alloush’s Jaysh Al Islam is the most powerful rebel group in Eastern Ghouta.

Tens of thousands of civilians trapped in the area suffer extreme shortages of food and medicine, activists say.

Syria’s war began as a peaceful revolt demanding democratic change, but later morphed into a brutal civil war after President Bashar Al Assad’s regime unleashed a massive crackdown against dissent.

More than 200,000 people have been killed since March 2011, and half the population has been forced to flee their homes.