Three people were killed and six wounded in a car bomb blast outside a popular restaurant in the centre of the Somali capital Mogadishu on Tuesday, police said.

Three people were killed and six wounded in a car bomb blast outside a popular restaurant in the centre of the Somali capital Mogadishu on Tuesday, police said.

The attack is the latest in a string of bombings in the war-torn Horn of Africa nation, where Al-Qaeda-affiliated Shebab militants are fighting to topple the government.

"There are at least three dead, and six others have been injured," police officer Ahmed Warhere told AFP.

"A vehicle loaded with explosives was parked outside the restaurant."

No one immediately claimed responsibility for the bombing, but the restaurant is located in the centre of Mogadishu, where the Shebab militants have carried out repeated attacks.

UN envoy to Somalia Nick Kay, who was visiting colleagues in the northeastern town of Garowe a day after the Shebab killed six people in an attack on a UN bus there, condemned "another atrocity".

He said the "killing needs to stop".

Four staff from the UN children's agency UNICEF were killed in the bus attack, including two Kenyans, an Afghan and a Ugandan. Two Somali security guards were also killed in that attack.