At least seven people were killed when a bomb exploded in a tea shop popular with government troops in the Somali town of Wanlaweyn on Saturday, officials and residents said.
Regional capitals and Western donors are nervous of any reversal of security gains made in Somalia by African Union peacekeepers in the fight against al Qaeda-linked militants, seen as a threat to stability in east Africa and beyond.
"The bomb killed seven people including civilians and soldiers and 12 others were seriously injured," Aden Olow, a witness, said.
"The lady who sold tea also died on the spot. I was going there to have tea but the explosion occurred shortly before I reached there. Most of the casualties were civilians."
Mohamed Nur Sidii, governor of the Lower Shabelle region where the town is located, about 90 km (55 miles) from the capital Mogadishu, said they were investigating the incident.