UN officials observing a fragile ceasefire in Syria reportedly came under fire on Tuesday in the northern region of Idlib.
Video footage has been released by activists which appears to show a large group of people surrounding UN vehicles, belonging to observers, before one starts to pour smoke from a crumpled bonnet.
The car appears to drive away from the incident, and it is not clear how many people were inside.
Reuters said that 21 people died in a series of attacks in the town of Khan Sheikhoun. It is thought the reported incidents are related.
The UN has not made any statement about the incident, however, and it was not possible for the Huffington Post UK to confirm or deny the claims.
One activist interviewed by The Guardian via Skype said that the monitors were observing a protest at the funeral of a man killed on Monday when regime soldiers opened fire.
"Four people were killed, dozens were injured, and the cars of UN monitors was targeted. One of the UN monitors was injured," he said.
But Reuters have since reported that the monitoring team were not hurt in the incident.
Elsewhere in Syria there were reports of large scale military activity by the rebel Free Syrian Army.
Meanwhile the Al Nasra group which was previously said to have claimed responsibility for a bombing in Damascus which killed 55 people last week said it had not carried out the bombing.
Since the uprising began in March 2011 more than 9,000 people have been killed according to the UN - while activists put the total dead closer to 13,000.
The Syrian government maintains it is fighting "armed terrorist groups".