Taliban fighters wearing army uniforms attacked US military vehicles in a parking lot in eastern Afghanistan on Wednesday, killing at least one policeman and torching several trucks, an official said.

The attackers detonated a car bomb outside the entrance to the facility at Torkham gate, a key crossing into Pakistan for NATO supplies leaving Afghanistan as the US-led coalition withdraws.

"During the three-hour fight with security forces, one police was killed, five wounded. Several vehicles were torched," Nangarhar provincial spokesman Ahmad Zia Abdulzai told AFP.

"All attackers, who had military uniforms on, were killed."

The parking lot was run by a private company and used by the US military for vehicles waiting to exit Afghanistan, he said.

NATO shipments through Torkham are currently suspended after Pakistani activists opposed to US drone raids forcibly searched trucks and threatened drivers.

A Taliban statement said their fighters had torched more than 30 US military vehicles on Wednesday.

Militants on both sides of the Afghan border frequently target NATO supply lines, forcing NATO to shift towards alternative routes via Central Asian countries.

The attack came a day after six US troops were killed and one wounded in a helicopter crash in southern Afghanistan.

NATO said there was no militant activity in the area of the crash, but the Taliban, who are waging a 12-year long insurgency to topple the US-backed Afghan government, said they had shot down the helicopter.