NATO fuel and supply trucks have been stranded along the border with Afghanistan since the Pakistani government closed the supply routes to protest a Nov. 26 NATO airstrike in its Mohmand tribal region that killed 24 Pakistani soldiers.
In the latest attack, the gunmen opened fire on eight oil tankers in an area 55 miles southwest of Quetta in Balochistan province, CNN reported, quoting police official Abdul Qadir.
One of the truck drivers was killed and the attackers blew up the tankers before escaping.
Pakistani Prime Minister Syed Yousuf Raza Gilani was quoted as telling the BBC in an interview that the supply routes could remain closed for weeks.
The stranded trucks have become a target of attacks by militants. Last week, militants destroyed more than 20 NATO fuel trucks outside Quetta.