Heavy fighting broke out between Somali army forces backed by African Union troops and Al Shabaab near the port town of Barawe town about 180 km (110 miles) south of Mogadishu.
The fighting flared up when Al Shabaab militants carried out an ambush attack on army base manned by the coalition forces, a local resident said.
He says heavy weaponry could be heard.
It remains unclear how many were killed in the fighting.
Neither Somali military nor Al Shabaab commented on the skirmish.