The incident occurred on Thursday when a massive blast ripped through a wedding party at Sona-Kay village.
Some 37 people were also injured in the explosion.
Somalia plunged into violence after warlords overthrew former dictator Mohamed Siad Barre in 1991.
The weak Western-backed transitional government in Mogadishu has been battling armed groups over the past years.
It has failed to restore peace despite the presence of thousands of African Union forces from Uganda, Burundi, and Djibouti.