An overturned oil tanker has burst into flames in Pakistan after a person tried to light a cigarette nearby, killing at least 150 people who had rushed to the scene of the highway accident to gather leaking fuel, an official says.

About 80 people were injured, with many suffering serious burns.

The tanker overturned after trying to make a sharp turn on the national highway on the outskirts of the city of Bahawalpur, about 100 kilometres southwest of Multan.

The tanker was driving from the southern port city of Karachi to Lahore, the Punjab provincial capital, when the driver lost control and crashed.

Nearby villagers ran toward the overturned tanker with jerry cans to take the leaking fuel, said Naseer.

Police tried to cordon off the area but were overwhelmed by the scores of villagers who pushed through to reach the truck.

Eyewitnesses said about 30 motorcycles that had carried villagers to the accident site lay in charred ruins nearby. Eight other vehicles were destroyed, they said.

Many of the bodies were burned beyond recognition, said Naseer.