Eighteen people have been killed and 25 wounded in a suicide bombing in Somalia.

Police captain Mohamed Hussein said the powerful explosion, thought to be from a car bomb, tore through shops and food stands in Mogadishu's Madina district on Sunday.

He said many of the wounded suffered horrific wounds. No group has yet claimed responsibility for the blast.

However, Somalia's homegrown Islamic extremist rebels, al-Shabab, often carry out such attacks.

Despite being ousted from large parts of south and central Somalia, al-Shabab continues to carry out guerrilla attacks in this Horn of Africa nation.

Earlier on Sunday it was reported that the group had vowed to continue fighting the Somali government and opposed the election of President Mohamed Abdullahi Mohamed.