Violence has escalated in Syria after the Arab League decision to halt its observer mission, with the government launching a campaign to re-take parts of Damascus that had fallen under rebel control.

Activists said at least 22 people were killed on Sunday, January 29 as the situation in the country continues to spiral out of control, taking the death toll in the last four days to at least 230.

Syrian state TV said "terrorists" had ambushed a bus carrying soldiers on a road south of Damascus. 16 were killed and a further six wounded in the attack, on Sunday.

An explosive device was detonated by remote control as the bus was travelling in the suburb of Sahnaya, some 12 miles south of the capital.

Activists said five civilians and a deserter were also killed as around 2,000 soldiers in buses and armoured personnel carriers, along with at least 50 tanks and armoured vehicles, moved at dawn into the eastern Ghouta area of Damascus to reinforce troops surrounding three large suburbs, Sky New reported.

Arab League chief Nabil al Arabi said on Saturday the mission was suspended after "consultations with Arab foreign ministers because of the upsurge of violence whose victims are innocent civilians."

There are fears of sectarian civil war following an increase in targeted assassinations and kidnappings and interior minister Mohammed al Shaar saying the authorities were determined to "cleanse" Syria and restore order. The UN estimates that at least 5,500 people have died since protests began 10 months ago against the rule of President Bashar al Assad.