Twelve Nato oil tankers have been set alight and four policemen killed when unknown gunmen opened fire in Talagang, a town in Pakistan's Punjab province.
Aslam Tarin, a Pakistani policeman, told Geo TV that the gunmen opened fire on the tankers and escaped after police returned fire,
Tarin said a nearby petrol station also caught fire due to Saturday's attack on the oil tankers.
Most oil supply to Nato forces in Afghanistan is transferred through Pakistan.
In a similar incident last October, six vehicles destined for Nato forces in Afghanistan, including one oil tanker, were attacked by about 30 gunmen in the Pakistani city of Peshawar.
Logistical difficulties
These incidents convey the difficulty of undertaking a war in a landlocked nation such as Afghanistan. About 75 per cent of supplies for the Afghan war are sent either through or over Pakistan, including 40 per cent of fuel for troops.
Supplies have become a focus of attack for fighters who aim to stem the resources available to Nato and US forces in Afghanistan.
Supplies along the Khyber Pass have regularly come under attack, forcing the US to find alternative supply routes.
The Khyber Pass is the mountainous border crossing between Pakistan and Afghanistan, notorious for its treacherous terrain and often lawless outlying regions.
PHOTO CAPTION
Pakistani security personnel stand beside burning NATO oil supply tankers after a bomb explosion in Khyber.
Al-Jazeera