MOGADISHU (REUTERS) - At least 10 people were killed in an explosion when a suicide bomber drove his car into a tea shop near the national security headquarters in Somalia's capital, a senior police officer said on Thursday.

No one immediately claimed responsibility for the blast, the second in almost a week in the city after Islamist militant group al Shabaab said it was behind an attack on the president's palace on Friday.

"A bomber swerved his car bomb into a tea shop where national security men were sitting and blew up. So far we have confirmed 10 people dead including national security forces and civilians. The tea shop was completely destroyed," Colonel Abdikadir Hussein, a senior police officer, told Reuters.

Mr Abdullahi Hassan, the district commissioner of Mogadishu's Abdiasis district, said the target of the attack was a national security car passing the tea shop.

A Reuters witness counted eight bodies.

On Friday, al Shabaab targeted President Hassan Sheikh Mohamud's heavily fortified palace in Mogadishu, known as Villa Somalia, in another blast and gunfight.

Al-Qaeda-allied al Shabaab ruled most of the southern region of Somalia from 2006 until 2011 when forces from other African nations sent by the African Union drove them out of Mogadishu and then expelled them from most urban centres.

The Islamist militants, who want to impose a strict version of Islamic law, still hold swathes of rural territory in southern Somalia and some smaller towns or villages, including the major coastal stronghold of Barawe.