"We were driving behind the UN convoy as protection when a roadside bomb exploded, wounding a first lieutenant and five troops," a soldier who asked to be identified only by his first name, Yahya, told AP at the scene.
At least three bloodied soldiers were rushed away.
The blast went off after the head of the UN observer mission, Major General Robert Mood, headed into the southern Syrian city with a team of observers and a convoy of journalists.
The explosion was more than 100 metres behind the convoy. It was not clear who was behind the blast.