DOUMA, Syria (Reuters) - A roadside bomb exploded on Sunday 150 meters from a United Nations convoy carrying the head of a Syria ceasefire monitoring mission in the town of Douma, a Reuters witness said.

Major General Robert Mood's car was stopped at an army checkpoint when the bomb detonated in an nearby alleyway and the convoy left, the Reuters journalist said, adding that there were no reports of casualties.

(Reporting by Khaled Al-Hariri; Writing by Oliver Holmes)