Mustaf Hagi Mohamed Mo'alin was gunned down by unknown assailants outside a mosque in the Wabari district late Saturday, police and witnesses said.

"Members of Parliament represent the voice of the Somali people and any attack on parliamentarians is an attack on the people, and it is unacceptable," Boubacar Diarra, special envoy of the AU commission for Somalia, said in a statement.

The attack came less than two weeks after President Hassan Sheikh Mohamud escaped an assassination attempt, two days after being sworn in by parliament. The Islamist al-Shabaab militia claimed responsibility for the attack.

On Saturday, over 200 al-Shabaab fighters surrendered to troops from the AU's AMISOM peacekeeping force. The AU said the insurgents were disarmed and taken into custody in Garsalem, about 80 kilometres from Mogadishu.

Eight militants were killed in the region in fighting before the surrender, the AU said.

At least 15 people were killed and at least 20 injured in a suicide bombing at a restaurant in Mogadishu on Thursday. Journalists and police officers were among the dead and injured.

Al-Shabaab, which controls large parts of the conflict-torn country claimed responsibility for the attack, which the United Nations Security Council condemned "in the strongest terms".

Germany's UN ambassador Peter Wittig on Saturday said the Security Council was committed to supporting the war-torn country in its bid to achieve peace and reconciliation. Germany currently hold's the rotating presidency of the Security Council.