Syrian rebel battalions from the Yousef al-Azma brigade in Idlib have surrounded a military encampment near the Syrian-Turkish border for four days, rebels told Reuters on Sunday (October 21).

The Free Syrian Army (FSA) fighters said they are trying to put pressure on the camp's approximately 150 soldiers to surrender.

FSA fighters unleashed a barrage of gunfire in the direction of the camp on Sunday.

Fighters took turns to fire bursts of machine gunfire while another fighter discharged rounds from a heavy machine gun mounted on the back of a pick-up truck.

One of the FSA fighters said the government troops were surrounded with no chance of escape.

Syria's conflict, which started with peaceful protests for reform, has escalated into a civil war marked by heavy use of artillery and air power by Assad's forces and regular bombings against symbols of his authority in Syria's main cities.

A car bomb killed 13 people in central Damascus on Sunday as President Bashar al-Assad told an international mediator seeking a truce in Syria's civil war that the key to any political solution was to stop arming rebels.

The bomb exploded outside a police station in the mainly Christian central Bab Touma district of the capital while Assad held talks with United Nations-Arab League envoy Lakhdar Brahimi, who is pushing for a temporary ceasefire to mark the Islamic festival of Eid al-Adha.

Speaking after his meeting with Assad, Brahimi gave few details of the talks but reiterated his call for a pause in the violence, which activists say has killed more than 30,000 people since the uprising against Assad erupted in March last year.

The violence has spread across Syria's frontiers. Assad's forces exchanged cross-border artillery fire with Turkey several times this month and on Friday (October 19) a huge car bomb in Beirut killed a top intelligence official whose investigations had implicated Syria in trying to stoke violence on Lebanese soil.