Officials in eastern Afghanistan say a bomb has exploded at a NATO base.

Authorities say attackers drove a vehicle full of explosives onto the base Friday in Khost province.

The French news agency quotes a security official as saying up to seven Afghans were killed in the attack.

Violence has surged across Afghanistan since the Taliban began its yearly summer offensive in April, vowing to target Afghan government and security forces, as well as the 130,000 foreign troops in the country.