At least 12 people were killed and a dozen more were wounded on Tuesday in an explosion that targeted a Tunisian military bus carrying presidential guards in the capital Tunis, in what the interior ministry said was a "terrorist attack".

Security and presidential sources said the explosion was an attack, adding that it was likely caused by a bomber detonating explosives inside the bus as it travelled along the tree-lined Mohamed V Avenue.

Interior Ministry spokesman Walid Louguini said that at least 12 people were killed and 16 wounded in what the government considers a "terrorist act".

Police fanned out throughout central Tunis after Tuesday's explosion, and ambulances rushed to the scene, evacuating wounded and dead.

The explosion came 10 days after authorities increased the security level in the capital and deployed security forces in unusually high numbers.

Tunisian authorities had recently announced the dismantling of a cell that it said had planned attacks at police stations and hotels in the seaside city of Sousse, about 150 kilometres (95 miles) southeast of Tunis.

Tunisia has suffered two major attacks this year targeting its tourism industry. A gunman killed 38 foreigners at a beach hotel in Sousse in June and in March, gunmen killed 21 tourists in an attack at the Bardo Museum in Tunis.

The Islamic State group claimed responsibility for both attacks

(FRANCE 24 with AP, AFP and REUTERS)