Heavy fighting has erupted in Syria's capital, Damascus, on Monday between the rebel Free Syrian Army and forces loyal to President Bashar al-Assad, the al Arabiya news network reported.
The sound of machine-gun fire and rocket-propelled grenades could be heard from the tightly guarded district of al-Mezze, witnesses said. The neighborhood is home to several security facilities.
The latest violence came a day after a car bomb in the northern city of Aleppo killed at least two people and injured 30 others.
On Saturday, at least 27 people were killed and another 97 wounded in two explosions in Damascus.
There were no Russian nationals among the dead, Russian officials said.
State TV described the blasts as "terrorist" attacks.
Meanwhile, a team of experts from the UN and the Organization of Islamic Cooperation has arrived in Syria to assess the humanitarian impact of the year-long unrest, which UN estimates say has left more than 8,000 people dead.
The government says more than 2,000 members of security forces have been killed combating "armed gangs and terrorists."
Opposition activists claim more than 200 Syrian soldiers have defected to the rebels in Damascus, al Arabiya said.
In a separate incident, activists said senior opposition figure Mohammed Sayyed Rassas was arrested and beaten by police after a rally in the capital on Sunday.
Security forces also held Farzand Omar, another opposition figure, as he arrived at Damascus airport.
