At least 21 people including four children were killed in an explosion which hit a vehicle in southern Syria, activists said.
The Observatory said six women were among the dead.
It was not immediately clear what caused the explosion, but activists in the area accused the military of planting a bomb in the ground along the road.
The Observatory said there is an army outpost in the area that is besieged by rebels.
Daraa was the birthplace of the Syrian uprising against President Bashar Assad in March 2011.