Heavy fighting raged on the outskirts of Damascus on Monday as elite troops backed by tanks tried to recapture a strategic suburb from rebels in one of the largest military operations in that district in months, opposition activists said.

Five people, including one child, died from army rocket fire that hit Daraya, the activists said. Daraya is one of a series of interconnected Sunni Muslim suburbs that ring Syria's capital and have been at the forefront of the 21-month-old revolt against President Bashar al-Assad.

"This is the biggest attack on Daraya in two months. An armoured column is trying to advance but it being held (back) by the Free Syrian Army," said Abu Kinan, an opposition activist in the area, referring to a rebel group.

He said that tens of thousands of civilians had fled Daraya during weeks of government assault but that 5,000 remained, along with hundreds of rebels. Daraya is located near the main southern highway leading to the Jordanian border 85 kms (50 miles) to the south.

Activists said the military is trying to push back rebels who have been slowly advancing from the outskirts of Damascus to within striking distance of central districts inhabited by Assad's Alawite minority sect.

Assad's forces have mostly relied on aerial and artillery bombardment, rather than infantry. Rebels have been able take several outlying towns and have clashed with government troops near Damascus International Airport, halting flights by foreign airlines.

Another activist in Damascus with connection to rebels, who did not want to be named, said Daraya has been a firing position for rebels using mortars and homemade rockets. From it, they have been able to hit a huge presidential complex located at a hilltop overlooking Damascus and target pro-Assad shabbiha militia in an Alawite enclave nearby known as Mezze 86.

"So far they have missed the palace but they are getting better. I think the regime has realised that it no longer can afford to have such a threat so close by, but it has failed to overrun Daraya before," he said. – Reuters