An explosion has hit the Old City of Damascus, killing at least 10 people and wounding dozens of other civilians, Syrian activists said.
It came as president Bashar Assad discussed the civil war in his country with visiting UN peace envoy Lakhdar Brahimi.
The blast targeted a police station in the Bab Touma neighbourhood, a Syrian official said.
Bab Touma, a popular attraction for shoppers, is inhabited mostly by members of Syria's Christian minority.
The British-based Syrian Observatory for Human Rights reported the death toll. It said it was not immediately clear if the victims were civilians or policemen but it described the blast as "strong" and said ambulances and police cars were rushing to the area.
Mr Brahimi, who represents the UN and the Arab League, met Assad in another part of the capital. Mr Brahimi has appealed for a truce between Assad's forces and rebels for the four-day Muslim holiday of Eid al-Adha, which begins on October 26.
Mr Brahimi arrived in Damascus on Friday after a tour of Middle East capitals to drum up support for the ceasefire, which he hopes will pave the way for a longer-term truce.
A range of countries including Iran, Iraq, Turkey and Germany have thrown their support behind the idea, but neither the Syrian government nor the rebels have signed on.
Mr Brahimi met foreign minister Walid al-Moallem on yesterday. A Foreign Ministry statement released after the meeting did not mention the proposed truce, but said the two men discussed "objective and rational circumstances to stop the violence from any side in order to prepare for a comprehensive dialogue among the Syrians".
Syrian government forces and rebels have both agreed to, and then promptly violated, internationally brokered ceasefires in the past, and there is little indication that either is willing to stop fighting now.