Afghan military officials say a suspected bomb has exploded among fuel tankers outside the main base for the U.S.-led coalition force in southern Afghanistan.

The officials say two fuel tankers exploded outside the base near Kandahar city early Friday, setting fire to eight others.

It was not immediately clear if there were any casualties.

The blast came amid a major surge in violence by Taleban-led rebels that has left more than 1,400 dead in the past six months and raised concern for Afghanistan's fragile democracy.

Violence has risen sharply in and around Kandahar, a former Taleban stronghold, with four suicide bombings in recent weeks and five medical aid workers killed Wednesday as they were returning to the city after treating people at a nearby refugee camp.