Islamabad, Pakistan (CNN) -- Militants on motorcycles attacked a convoy of tankers carrying fuel for NATO in northwest Pakistan Tuesday, igniting four of the trucks and injuring at least one of the drivers, police said.
The trucks were traveling through the Mastung district about 50 kilometers (31 miles) south of Quetta when militants shot at the convoy, igniting a fire, senior police official Ismail Kurd said.
The trucks were carrying fuel for NATO troops, but apparently do not belong to the organization.
Mastung has been the site of repeated violence between extremist Sunni and Shiite Muslims in the past few months. Last week, militants attacked a bus carrying Shiite Muslims, killing 26 and wounding six, police said.
Smoke and flame rise from burning NATO supply trucks after they were attacked by armed militants on the outskirts of Quetta on September 27, 2011. Gunmen in southwestern Pakistan attacked three oil tankers and a container carrying supplies to NATO (Getty)