MOGADISHU (Reuters) - A suicide car bomber from Somalia’s Islamist group al Shabaab hit a military convoy outside Mogadishu on Tuesday, causing an unknown number of deaths, a police officer and the group’s spokesman told Reuters.

The attack targeting a passing military convoy occurred in Afgoye, a district about 30 km northwest of Mogadishu, police officer Major Abdiqadir Ali said.

“What we are sure (of) is a military vehicle was hit,” Ali said, adding there were casualties but the death toll had not yet been determined.

Al Shabaab’s military operations spokesman Abdiasis Abu Musab told Reuters they were responsible for the attack.

The group, an ally of Al Qaeda, is fighting to topple the country’s western-backed central government and impose its rule based on its own interpretation of sharia law.

Al Shabaab also wants to force out an African Union-mandated AMISOM peacekeeping force that is helping defend the government of President Mohamed Abdullahi Mohamed.

“One of our mujahideen (was) martyred after he rammed his car into a Somali military convoy,” Abu Musab said.

One military pick-up truck was destroyed while 12 soldiers were killed by the blast, he said and added that a second vehicle in the convoy was also damaged.

The soldiers in the convoy were U.S.-trained Somali military commandoes. Al Shabaab have targeted them on the same road several times in the past.