Syrian troops have been battling Free Syrian Army rebels for control of a military airbase on the outskirts of Damascus, according to opposition groups.
The rebels captured a "large part" of Marj al Sultan airport, 15 kilometres (nine miles) east of Damascus, and destroyed two helicopters, the Syrian Observatory for Human Rights said.
The Britain-based group, which relies on a network of activists, lawyers and medics for its information, said 31 rebels and 16 soldiers were killed in the battle.
Meanwhile, regime forces used helicopter gunships to shell the northeast and southwest outskirts of Damascus, the Observatory said.
The latest military activity comes as Russia and France prepare for talks in Paris next week aimed at addressing their differences over the conflict.
Key to the talks will be what is seen as the West's impatience for regime change by the removal of President Bashar al Assad from power.
"There is a major disagreement," Russia's envoy to Paris, Alexander Orlov said. "The West says it (a solution) must start with the departure of Bashar al Assad - but we say this is where it must end".
Turkey and Iran, who also hold opposing views on a solution to the conflict, held private talks on Saturday.
Russia and China have previously blocked UN Security Council efforts aimed at increasing pressure on the Assad regime.
In the face of the revolt, Assad's regime has been reducing its territorial ambitions to focus on Damascus, central Syria and Alawite bastions, as it digs in for a long war, according to analysts.
More than 40,000 people have been killed in 20 months of conflict between Syrian regime forces and rebels fighting for his overthrow, according to monitoring groups.
Although the conflict is usually seen as being between an opposition led by the country's Sunni Arab majority and the minority Alawite-dominated regime, the struggle is as much a matter of social class as it is ethnicity.