A suicide bomber blew up a vehicle at a bus stop west of Damascus on Tuesday, killing at least 15 people, state television said.
"The terrorist explosion in front of the bus stop in Somariyeh was caused by a suicide attacker," the broadcaster said in a news flash.
"It killed at least 15 citizens and wounded more than 30."
The Syrian Observatory for Human Rights said two children were among the dead.
"Nine of those killed were civilians, while six were troops," said the Britain-based Observatory, which relies on a network of activists, doctors and lawyers on the ground for its reporting.
Somariyeh neighbourhood is home to "a complex housing families of soldiers fighting with the elite Fourth Division," Observatory director Rami Abdel Rahman told AFP.
The Fourth Division is commanded by President Bashar al-Assad's feared brother Maher.
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The bombing came after mortar fire on several parts of Damascus killed six people, including two children, the Observatory said.
It also came as rebels, including Al-Qaeda loyalists, pressed a four-day-old offensive to lift a year-long siege by the army of their positions in eastern suburbs of the capital.
Fighting raged in Adra, a strategic town northeast of the capital, while the army pounded the besieged rebel enclaves of Douma and Marj to its east, the Observatory said.
Lebanese Shiite militant group Hezbollah has sent "hundreds of fighters" to back the army in its bid to repulse the rebel assault, the watchdog added.
Fighting also raged in the Qalamoun mountains north of Damascus, a border area where the army has been battling to cut rebel supply lines to neighbouring Lebanon.
Health Minister Saad al-Nayef accused the rebels of killing "five doctors, five nurses and two ambulance drivers" in the Qalamoun town of Deir Attiyeh after they seized it from the army last week.
In Nabuk, another rebel-held town in the region, government air strikes killed at least seven people, among them three children, the Observatory said.