UN observers were surrounded by protesters who were subsequently fired on by government troops during their mission to monitor a fractured truce in the country.
An advance party of six UN peacekeepers in blue berets was surrounded in Erbeen, near the capital Damascus, activists reported.
A crowd of around 5,000 people denouncing President Assad's regime swarmed the cars before the sound of automatic gunfire sent them running for safety.
Colonel Ahmed Himmiche of Morocco, who is leading the UN mission, said that the shots were not aimed at the monitors' cars.
Footage of the incident was posted on YouTube, and echo similar scenes during an Arab League monitoring mission which fell apart in January.
One protester told the activist network Avaaz: "We gathered in the courtyard of the municipal building in Erbeen and demonstrators surrounded the UN cars and began shouting anti regime slogans.
"The security forces threw tear gas at us and some of the people took shelter behind the United Nations vehicles but the cars fled the area and the security forces began shooting at the demonstrators.
"Around 10 people were injured, two were shot in the chest and one of the observers was beaten."
It was not possible to verify the information independently.
UN Secretary General Ban Ki-moon has said the party of 250 observers will not be enough to keep the peace in Syria, but the regime has denounced plans to increase the numbers.
Activists reported continued violence across the country, including in Homs where Avaaz said up to 7 people were killed.
Video was posted appearing to show rockets landing on the city and exploding in residential neighbourhoods.
One activist said: "Dark clouds cover the city of Homs and the remaining people in Homs are demanding the observers come to Homs urgently, because what is happening here is a genocide."
Elsewhere it was reported that emails written by the leader of the SNC had been hacked and would be published by Al Akhbar.
Meanwhile the wives of the British and German representatives to the United Nations have released a video calling on the wife of the Syrian president to help stop the country's violence.
The video, released on video-sharing website YouTube, asks viewers to sign a petition urging Asma Assad to speak out against the bloodshed.
The online petition has so far received more than 2,000 signatures.
The UN has said more than 9,000 people have been killed in Syria since the start of the 13-month uprising.
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