A suicide bomber has rammed a truck filled with explosives into a government building in central Somalia, causing an unknown number of casualties.

The Somali militant group al-Shabab has claimed responsibility for the attack, which occurred Tuesday in the town of Beledweyne, about 30 kilometers from the Ethiopian border.

Local officials say the bomber targeted a building that houses Somali government officials and pro-government Ethiopian soldiers. Somali officials say guards fired on the speeding vehicle in a failed attempt to stop it from entering the compound.

Al-Shabab says several people were killed. Somali officials have not confirmed any deaths or injuries.

The Ethiopian military typically does not release casualty figures.

Al-Shabab is fighting to overthrow Somalia's U.N.-backed transitional government and impose strict Islamic law. It is battling African Union forces in Mogadishu, as well as Kenyan soldiers in the south and Ethiopian troops in the west.