Checkpoints every 300 metres, walls of sandbags, sounds of gunfire and the rumbling of tanks: the towns of Harasta, Douma and Sakba, all less than 15 km north of Damascus, are under siege.

"We apologise but this road and all access to Douma is blocked until further notice," a Syrian soldier at the entrance to Harasta said without offering further explanation.

Opposition fighters briefly took control of Douma on January 21 only to later retreat after a brutal push back by Syrian forces.

Intense war

At least 66 people, including 26 civilians, were killed in violence across Syria on Sunday, the Syrian Observatory for Human Rights said.

The London-based rights group said 26 soldiers, five other members of the security forces, nine army deserters were also among those killed as the regime cracked down on protesters and rebels.

And since Thursday Douma and the surrounding towns have come under an intense army offensive against the increasing ranks of deserter fighters who have taken up arms in these distant suburbs of the capital.

Narrow streets are often flooded by the hard winter rain and at night, when electric power is almost always cut, the area is pitched in darkness with sounds of gunfire in the distance signalling another round of fighting.

"Last week I was surprised by a Free Syrian Army checkpoint that was controlling traffic in the Ain Terma neighbourhood (near Douma)," said Rami, an architect based in Damascus.

"This region is partly out of government control," he said.

Street after street fighting

The Free Syrian Army, based in Turkey, claims 40,000 fighters and that its ranks are swelling with desertions from the military.

Still, street after street, regime soldiers take positions behind sandbags, setting up checkpoints at strategic intersections in search of armed fighters or suspects wanted by security services.

In these battle-worn towns, traces of machine-gun fire scar the walls. The crumbling facade of a 10-storey government building shelled by rocket fire is testimony to the intensity of the fighting.

A billboard reads: "I support the law". Another says: "The Syrian people are a united people. May God protect them".

Driving past Harasta on the country's main highway, urban density quickly gives way to patches of vacant lots and grassy fields, a setting conducive to the night-time movements of rebel fighters.

10 months of unrest

"They hide during the day and attack at night," a Harasta resident said.

Hundreds of soldiers now surround the area in all directions, armed and ready to cut off any rebel manoeuvres.

Closer to Damascus to the south, in the restive suburbs of Jaramena and Mleha, all roads heading north are under strict surveillance.

It has been more than 10 months since the protest movement against the regime of President Bashar al-Assad began.

The movement, inspired by the Arab Spring uprisings across the region, has turned into an insurgency that the United Nations says has killed thousands, felled by the government crackdown and almost daily scenes of urban warfare.

The regime, which denies the contestation is widespread, says opposition fighters are terrorists backed by foreign powers.