Syrian activists say at least 31 people have been killed in a car bombing near the headquarters of the country's ruling Ba'ath Party in central Damascus.
The Britain-based Syrian Observatory for Human Rights said Thursday most of the dead were civilians.
Syrian state media called the blast a "terrorist bombing" that struck a densely populated area near the al-Mazraa neighborhood.
Russian news agencies also said the bombing blew out windows at the Russian embassy.
Meanwhile, the Syrian opposition is holding a meeting Thursday in Cairo to discuss an initiative to hold peace talks with President Bashar al-Assad's government.
On Wednesday, Syrian activists said rebels shot down a warplane outside Damascus, shortly after an airstrike killed at least 20 people in the same area.
Amateur video circulated by the Syrian Observatory for Human Rights showed a warplane firing rockets and then plummeting to the ground in Hamouriya after apparently being hit by rebel machine gun fire. The shoot-down could not be independently verified.