Clashes between forces loyal to Syrian president Bashar al-Assad and rebels outside Damascus on Tuesday resulted in dozens killed.
Activists say the bloodletting outside the capital marks the worst violence in the suburbs of Damascus since a popular uprising against Assad's rule began 16 months ago.
The Syrian state news agency SANA said "armed terrorist groups" had blocked the old road from Damascus to Beirut.
"The clashes led to the killing of tens of terrorists, wounding a large number of them, arresting others and seizing their weapons which included RPG launchers, sniper rifles, machineguns and a huge amount of ammunition," the agency said.
The London-based Syrian Observatory for Human Rights reported heavy fighting near the Republican Guard headquarters in Qudsiya, and in the Damascus suburbs of al-Hama and nearby Mashrou' Dumar.
"Violent clashes are taking place around positions of the Republican Guard in Qudssaya and Al-Hama," eight kilometers from central Damascus, Rami Abdel Rahman, who heads the Observatory told AFP.
"This is the first time that the regime uses artillery in fighting so close to the capital," he said. "This development is important because it's the heaviest fighting in the area and close to the heart of the capital."
"Intense shelling by the Syrian regime and also intense clashes with rebels fighters in [Al-Hamaeh town]. Also, sounds of explosions in the suburbs of Doumar and Qudssaya, areas outside of Damascus," the Revolution Leadership Council of Damascus reported.
"Continuous ... shelling, sounds of gunfire, and snipers on building rooftops [in Al-Hamaeh]," it added.
"Telephone landlines and cell phone lines are disconnected, in addition to electricity cut off. Military reinforcement is on the way to the area now."
The revolt against Assad's rule has crossed from resistance to all-out civil war in recent months. At least 10,000 people have been killed since March 2011, according to the United Nations.
However, diplomats say the actual number is much higher.
The 300-strong U.N. monitoring mission was suspended 10 days ago because it was considered too dangerous to carry on sending teams out to supervise a truce that exists on paper only.
U.N. special envoy Kofi Annan, who crafted the failed ceasefire and monitoring plan in April, wants the five permanent members of the U.N. Security Council and governments with influence on Assad.
Annan says Assad's ally Iran should be at the table, but the involvement of Tehran is opposed by the United States, Britain and France.