"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", Daily News reports.

"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 ... in retaliation for the regime's raids against our people in the Eastern Ghouta area," Alloush wrote.      

Alloush's Jaysh al-Islam is one of rebel group in Eastern Ghouta.      

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