The vehicle, laden with explosives, targetted government soldiers as it went off at the centre of Baidoa town, a provincial capital of Bay region in south of Somalia, Xinhua reported.
The explosion left 13 people dead and more than 20 others were injured," police officer Must Elmi said.
The dead included three government soldiers, who were in the vicinity of the blast, the deadliest in the town since government forces and African Union peacekeepers took control from militants Al-Shabaab fighters back in 2011.
The town is largely closed and movement is restricted in and around the area of the explosion as well as near government and African Union peacekeeping Mission (AMISOM).
No group immediately claimed responsibility for the attack.