A suicide bomber in Somalia killed 12 civilians and left a further 27 wounded after ploughing an explosives-laden car into a convoy of African Union (AU) troops on Monday.

"The car packed with explosives hit one of the armored trucks," local governor Adukadir Mohamed Sidi told Agence France-Presse (AFP) news agency.

Two AU soldiers were reportedly among those wounded in the attack.

A second suicide attack an hour later on the same road southwest of the capital, Mogadishu, wounded two people traveling in a Somali government convoy of police and security forces, according to a senior police officer quoted by Reuters news agency.

Islamist militant group al-Shabab has now claimed reponsibilty for the attacks, which are the first since the group vowed to avenge the killing of its leader Ahmed Abdi Godane last week. The Pentagon confirmed on Friday thatGodane was killed in a US airstrike.

"We are behind the two car bombs driven by mujahideen (fighters)," said Sheikh Abdiasis Abu Musab, spokesman for al-Shabab's military operations.

Enormous explosion

Reports from AFP said witnesses had seen a huge blast and wave of fire, with civilians on the busy highway caught up in the explosion.

"I saw two minibuses with pools of blood. Many civilians were killed. The explosion was enormous," said one witness, Ali Muhidin.

The AU currently has some 22,000 troops battling militants in Somalia.

On Monday, prosecutors in Germany alleged that three men arrested at Frankfurt airport were members of al-Shabab. The German nationals were taken into custody after returning from Kenya.

ksb/tj (Reuters/AFP/AP)