Syrian state TV says foreign-sponsored insurgents have killed at least 20 people in a suburb of the capital, Damascus.
The development comes as Syrian security forces discovered a mass grave near the capital on Saturday.
Bodies of civilians and Syrian army members were found in the mass grave.
Meanwhile, the Syrian troops have killed a large number of terrorists in clashes between government troops and insurgents across the country over the past few days.
Also on Saturday, Syrian security forces in the western province of Hama killed dozens of insurgents during clashes in the town of al-Rastan, about 184 kilometers (114 miles) north of Damascus.
In addition, fighting continues on the outskirts of the northwestern city of Aleppo and the Syrian army has inflicted heavy losses on insurgents.
The latest development comes two days after Kofi Annan announced that he will resign as the UN-Arab League special envoy to Syria at the end of August.
The Syrian Foreign Ministry expressed regret about the resignation of Annan.
On August 1, Syrian President Bashar al-Assad said the country is engaged in a “crucial and heroic” battle that will determine the destiny of the nation.