Unidentified people pelted a UN observers' convoy with stones on Friday near a suburban area of Syrian capital city of Damascus, Xinhua reported.
According to witnesses, the convoy was pelted with stones while heading toward the suburb of Dumair, northeast to Damascus, before it reached a military checkpoint at the entrance of Dumair.
One of the UN vehicles was slightly damaged with smashed window, they added. However, none of the observers was injured.
Last Wednesday, a roadside bomb ripped through the UN convoy while it was en route to Daraa province, injuring eight members of the accompanying security forces.
Meanwhile, UN observes' spokesman said Friday that 150 observers, 105 of whom being unarmed military monitors, are now on ground in Syria.
The observers arrived in Syria last month to monitor the implementation of six-point plan brokered by UN-Arab League joint special envoy Kofi Annan, which has called mainly to halt violence from all sides to pave the way for a political settlement to Syrian crisis.
The head of the rebel Free Syrian Army has recently said that UN observers have become "perjurers," and added that his forces will not stay calm for long.
Earlier Friday, anti-regime protests erupted in several Syrian cities, hailing the armed rebels and urging people to take up arms.