A suicide attacker has rammed a bomb-laden car into a police station in the Somali town of Afgoye, killing at least four police officers, before militants then stormed the area, local authorities say.
"Many militants have entered the town. Heavy fighting is taking place," police major Nur Osman told Reuters on Tuesday.
Afgoye is about 30 kilometres southwest of the capital Mogadishu.
The al-Shabab militant group, which has been carrying out a series of deadly bombings throughout Somalia, claimed responsibility for the attack.
The group is fighting to topple the Western-backed government in Mogadishu.
"Now most of the town is under our control," Sheikh Abdiasis Abu Musab, al-Shabab's military operations spokesman said.