Aslam Tarin, a Pakistani policeman, told Geo TV that the gunmen opened fire on the tankers and escaped after police returned fire,
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.
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.
Several NATO oil tankers were set on fire in the Punjab province of Pakistan, and four policemen were killed in a gunfight with unknown gunmen yesterday, reports say. The  (DPA) news service attributes the attack to the Taleban.

The incidents occurred in the town of . Aslam Tareen, the regional police chief, said that "around a dozen" tankers were set on fire after being attacked with rocket-propelled grenades. "Later on, they exchanged intensive fire with the police and killed four of our officers while two more were injured," Tareen said, adding that a petrol station nearby the oil tankers also caught fire.

DPA says the attack was the deadliest on NATO supply convoys in the province. Close to three quarters of all oil, food, and military supplies to landlocked Afghanistan first pass through Pakistan.