No causalities have been reported so far.

Gunfire was heard briefly outside Premier Bank after the explosion - shots thought to have been fired by nearby security guards.

Fire engines have now extinguished the flames.

It is believed that an explosive device may have been planted on the vehicle, which belonged to the bank.

Somalia has been unstable since the fall of the Siad Barre regime in 1991.

Islamist al-Shabab militants, fighting the UN-backed government, often launch attacks in the city.