ISLAMABAD:  A fiery crash between an oil tanker and a passenger bus killed at least 20 people in Pakistan, a police spokesperson and media said on Tuesday.

It was not immediately clear what caused the crash late Monday night or early Tuesday on a motorway near the central city of Multan.

The bus and tanker caught fire after the collision, a police spokesperson said in a statement, without providing details on the number of fatalities.

Geo and Dunya TV reported at least 20 people were killed.

Six passengers survived, an official of a state-run rescue service told Dunya TV on the spot.

"The fire was raging when we got here," he said.

(Reporting by Asif Shahzad in Islamabad and Syed Raza Hasan in Karachi; Editing by Stephen Coates)