Armed groups launched an assault on Tuesday at the Syrian government troops in the Damascus suburb of Douma, killing one army personnel and leaving three others injured, state-run SANA news agency reported.
The armed men fired RPG shells at civilians and law-enforcement forces in Douma, leaving many injured, said SANA, Xinhua reported.
Douma, some 10 km northwest of the center of Damascus, has emerged as a hotspot of armed insurgency against the government troops.
Earlier in the day, UN observers who arrived in Syria 10 days ago to oversee a cease-fire toured Douma and met with people there.
The 11-member UN observer team continued their tours in different hotspots in Syria and the deployment of 300 observers would be completed over the next few weeks.
Syria has repeatedly declared its commitment to the peace plan brokered by international envoy Kofi Annan, but also accused " armed groups" of escalating their violent acts to stymy Annan's efforts.
Syria reported a surge in murders and kidnappings by armed groups in the country since the UN observers' arrival.