Blast damages UN vehicles in north-west Syria
15 May 2012 Last updated at 22:34 BST
Three UN observer vehicles have been damaged in a blast in the north-western Syria town Khan Sheikhoun, but the observers were not hurt, the UN said.
Activists say that at least 20 people have been killed by Syrian security forces in the town during the UN visit.
This video, which cannot be independently verified, purports to show the incident where the UN convoy was struck by an explosion from an improvised explosive device.