The blast occurred in the busy market in the town of Wanlaweyn in the Lower Shabelle region, about 90 km (55 miles) to the northwest of the coastal capital Mogadishu.
Given Wanlaweyn’s lack of hospitals able to take in multiple casualties, residents said they took many of the wounded to their homes for the time being after the afternoon blast near a busy cluster of khat kiosks.
Police said they were investigating whether the explosion was caused by a planted bomb or by a suicide bomber.
“The blast at the khat kiosks killed at least five civilians and injured more others including soldiers. We are investigating whether there are more casualties and the cause of the blast,” police Captain Farah Ismail told Reuters.
“The death toll may rise,” he added.
Residents said the kiosks were busy with soldiers buying khat. “I counted five dead people, including two shoe shiners, a mother who sold khat and two customers. There were 10 other injured civilians,” shopkeeper Ahmed Mohamud told Reuters.
“I could also see several soldiers in uniform being transported from the blast scene but I could not confirm whether they were dead or wounded.”
Abdiasis Abu Musab, al Shabaab’s military operation spokesman, said the group was behind the attack and that its target was the soldiers.
Al Shabaab is fighting to overthrow Somalia’s central government and establish its own rule based on its interpretation of Islamic law.
Since being pushed out of Mogadishu in 2011, the group has lost control of most of Somalia’s cities and towns. But it retains a strong presence in regions outside the capital.