A suicide car bomb rammed into a local government office in Somalia's capital Mogadishu on Monday causing casualties, a police officer told Reuters.

A Reuters witness saw huge clouds of smoke above the city following a loud blast and gunfire.

"A suicide car bomb rammed into the office of Hodan district of Mogadishu. There are casualties but so far we do not have a figure," major Mohamed Nur, a police officer, told Reuters.

Witnesses said the office was destroyed.

"A speeding 4x4 car ran into the district office," witness Hussein Osman told Reuters. "I ran away and now I see from far the office completely destroyed. I see ambulances carrying casualties but I cannot make out how many dead or injured. I could see five people being taken by ambulance."

Last week, a suicide car bomb destroyed another district office of Mogadishu.

There was no immediate claim of responsibility for the attack.

Al-Qaeda-linked al-Shabab frequently carry out bombings and gun attacks in the capital Mogadishu and other parts of Somalia.

They are fighting to topple Somalia's Western-backed central government and establish their own rule based on their strict interpretation of Islamic law.