Afghan officials say a truck bomb has exploded outside a U.S.-led military base in eastern Afghanistan.

Police say a suicide truck bomber approached the heavily fortified entrance of the base early Thursday and detonated his explosives after being confronted by Afghan security guards.

The Associated Press quotes NATO as saying that two Afghan guards were killed in the blast.

The Taliban has claimed responsibility for the attack, which happened at a U.S.-run provincial reconstruction team base in Gardez, the capital of the eastern province of Paktia.

Violence in Afghanistan is at its worst since the U.S.-led invasion in late 2001, with international troop and Afghan civilian deaths reaching record levels.