The move comes days after the Syrian government warned opposition militants to hand over their weapons or they would face a military offensive.
On Saturday, the head of the UN observer team in Syria announced the suspension of its activities, due to the escalation of violence.
The first team of UN observers arrived in Syria on April 15 to monitor a ceasefire that took effect three days earlier and was part of a six-point peace plan brokered by UN-Arab League envoy, Kofi Annan.
Meanwhile, residents of the retaken Syrian village of al-Haffeh in the Latakia Province say armed gangs forced them to protest against the government.
The army took back the northwestern town of al-Haffeh from terrorists after heavy fighting, at the request of the residents. Armed groups attacked civilians and burned down and sabotaged public and private properties there.
The unrest in Syria began in March 2011. Many people, including security forces, have been killed in the turmoil.
The West and the Syrian opposition accuse the government of killing the protesters, but Damascus blames “outlaws, saboteurs, and armed terrorist groups” for the unrest, insisting that it is being orchestrated from abroad.
Militant groups in Syria have repeatedly requested heavy weapons from their foreign supporters. Many US politicians have also called for arming the anti-government groups in Syria.