A car bomb exploded in the heart of the Somali capital Mogadishu on Tuesday, witnesses said, the latest in a string of deadly attacks in the coastal city.

The suicide attack piles yet more pressure on a government that relies on African troops to prop it up and controls little of the country where it is fighting an Islamist insurgency.

Smoke was seen rising from the blast near an old cinema between the Turkish embassy and the Kilometre 4 (K4) junction, a busy intersection in Mogadishu's administrative district.

Gunfire could be heard in the immediate aftermath of the explosion and ambulances streamed through the streets.

The explosion happened near K4 and I've seen three wounded people being carried away from the scene of the explosion, Nimca Hussein, a resident in the area, said.

She said government and African Union soldiers were dispersing people from the scene.

A traffic policeman told Reuters that the security forces had earlier stopped a vehicle.

The troops tried to question the driver and take photographs when the suicide bomber detonated his bomb, Abdiweli Elmi, a policeman on patrol at the junction said.

He said there were numerous casualties. I saw the bodies of two policemen and one civilian, Elmi said.

(Reporting by Mohamed Ahmed; Writing by Richard Lough; Editing by David Clarke and Louise Ireland)