A suicide truck bomber attacked a US-run base on Friday, sparking clashes that killed up to 14 people in eastern Afghanistan near the Pakistani border, officials said.
NATO's US-led International Security Assistance Force (ISAF) said none of its personnel was killed in the attack in Khost province, a Taliban flashpoint that borders Pakistan.
The Taliban militia, which is leading a 10-year insurgency against foreign troops and the Kabul government, claimed responsibility for the attack.
But the precise details of what happened were murky.
An Afghan security official said that the bomber drove a truck packed with explosives into the outer security checkpost of Forward Operating Base Salerno, which is run by the US military.
"Initial information shows that seven Afghans have been killed and 13 others injured," the official said on condition of anonymity because he was not authorised to speak to the media.
According to the official, the victims are Afghan workers involved in a construction project at the base.
But Khost provincial police chief Sardar Mohammad Zazai later told AFP that only three attackers were killed as they stormed the base.
"Four civilians were injured when the roof of a nearby house collapsed as a result of the explosion," Zazai said, adding that the bodies of three attackers had also been recovered.
ISAF, however, said 14 insurgents were killed in clashes, but released no further details. It said it did not have further details on any civilian casualties.
A spokesman for the Taliban claimed that a "large number" of foreign soldiers were killed, but the militia is known to exaggerate its claims.
"One of our mujahideen rammed a vehicle packed with ten tons of explosives into a NATO base in Khost city and detonated the truck near the restaurant of the base", said Taliban spokesman Zabiullah Muhahid said.
FOB Salerno is close to FOB Chapman, another US-run base in Khost where an Al-Qaeda triple agent blew himself up killing seven CIA agents and his Jordanian handler in December 2009, the deadliest attack on the US intelligence agency since 1983.
On August 28, 2010 NATO said about two dozen Taliban militants were killed in a failed attempt to storm both US-run bases in a city in eastern Afghanistan, NATO said.
Khost is one of the most volatile parts of the country.
It shares a porous border with Pakistan's tribal belt, which lies outside government control, and where US officials say the Taliban and al-Qaeda have carved out rear bases for operations in Afghanistan.
Khost province borders Pakistan, which is widely believed to be a key source of fighters, funds and supplies for the Taliban.