A car bomb exploded near a police station in the central Bab Touma district of Damascus on Sunday, witnesses said, and state television said at least 10 people were killed.

Ambulances sped to the site and security forces cut off access to the area. Several cars were burnt, the witnesses said.

The explosion took place as President Bashar Assad was meeting international envoy Lakhdar Brahimi, who has called for a temporary truce in Syria's civil war.

Brahimi, the joint UN-Arab League special envoy for the Syria crisis, has been criss-crossing the region with the aim of convincing Assad's main backers and his foes to support the idea of a truce during the holiday, which starts at dusk on Thursday.

He held talks on Saturday with Syria's Foreign Minister Walid al-Moualem, which the ministry described as "constructive and serious".

Syria has so far given a guarded response to Brahimi's ceasefire proposal, suggesting it wants guarantees that rebels would reciprocate any move by Assad's forces.

Damascus residents said Assad's forces shelled several districts on the edge of the Syrian capital overnight. The Syrian Observatory for Human Rights, which monitors violence across the country, said 140 people were killed in Syria on Saturday.