Reports from Syria say government forces have ambushed and killed a large number of Islamist rebel fighters in the eastern outskirts of Damascus.
Syrian state media says more than 170 rebels were killed. The British-based monitoring group the Syrian Observatory for Human Rights says it has received reports that at least 70 people died.
The observatory, which is close to the rebels, also says about 3300 people had been killed in fighting between rebel factions so far this year.
The Eastern Ghouta, a collection of rural towns outside Damascus, is a rebel stronghold where Syrian forces are believed to have carried out a chemical weapons attack last year.
Some analysts suggest Wednesday morning's army operation - said to have taken place near Otaybeh village - may have tightened President Bashar al-Assad's grip on Damascus.
Meanwhile, the international chemical weapons watchdog has welcomed the removal of the latest consignment of toxic chemicals from Syria.
The country missed its deadline for removing its chemical arsenal earlier this month but the Organisation for the Prohibition of Chemical Weapons says a consignment of mustard gas was shipped out of the Syrian port of Latakia on Wednesday.
