A bomb has exploded outside a police station in the Old City of Damascus, killing 13 people and wounding many others, Syrian state media and officials say.
Ambulances sped to the site and security forces cut off access to the area. Several cars were burnt, witnesses said.
State news agency SANA said the blast was caused by an explosive device planted under a car by an "armed terrorist group" - the term the regime uses for the rebels seeking to topple President Bashar al-Assad.
Video posted online showed several burnt-out cars and destruction near Bab Touma, one of the seven gates of the historic Old City.
An Associated Press news agency reporter at the scene said he saw blood stains in the street and on the pavements. He said glass windows of several shops in the area were shattered and at least four cars were completely burnt.
The explosion in the mainly Christian neighbourhood took place as Assad was meeting Lakhdar Brahimi, the UN-Arab League envoy, in another part of Damascus.
Brahimi has called for a ceasefire during the Muslim Eid al-Adha holiday beginning on Friday to stem the bloodshed in a 19-month-old conflict which the opposition says has killed at least 30,000 people.
"I appeal to everyone to take a unilateral decision to cease hostilities on the occasion of Eid al-Adha and that this truce be respected from today or tomorrow," he said in Damascus after meeting Assad.
In Sunday's other violence, clashes and shelling were reported in the Damascus suburb of Harasta, and bombardment in nearby Douma and Zamalka.
Fighting was also reported in the northern city of Aleppo, a key battleground for the past three months.
Brahimi said the ceasefire call was his "personal initiative, not a blueprint for peace".
"This is a call to every Syrian," he said, adding that he had contacted the leaders of the political opposition both within and outside Syria, and armed groups inside the country.
|Brahimi, right, met Assad after touring Middle East capitals
to gather support for an Eid truce [Reuters]
"We found them to be very favourable" to the idea of a truce, he said.
Brahimi met Walid al-Muallem, Syrian foreign minister, and some opposition leaders tolerated by the Assad regime on Saturday to push for a truce over the four-day Eid holiday.
A foreign ministry statement released after the meeting did not mention the proposed truce, but said the two men discussed "a halt to the violence ... in order to prepare for a global Syrian dialogue, free of any foreign intervention.
"Such a dialogue is the only way to emerge from the crisis," it said.
Brahimi arrived in Damascus on Friday after a tour of Middle East capitals to build support for the ceasefire.
A range of countries including Iran, Iraq, Turkey and Germany have thrown their support behind the idea.
Syrian government forces and rebels have in the past both agreed to and then promptly violated internationally brokered ceasefires, and there is little indication that either is willing to stop fighting now.