'Presumably a remote-controlled bomb hit an oil tanker, triggering a blaze that quickly engulfed other trucks,' Basheer told DPA by phone.

A gunfight between the paramilitary forces and the attackers ensued.

A charred body believed to be that of a driver was found in one of the gutted oil tankers, while at least one soldier was wounded in the clash.

The highway running through Chaman is one of the two main supply routes used by contractors to ferry fuel and military supplies from Pakistan's southern port city of Karachi to the US and NATO troops in landlocked Afghanistan.

Militants have staged relatively fewer attacks on the Chaman road link than on the main Khyber Pass route in Pakistan's north-western tribal region.

Pakistani authorities had increased checking of lorries coming from Afghanistan since April 4 after around 50 Afghans, who were being smuggled to Iran via Balochistan, were found dead in a container truck left abandoned in the provincial capital Quetta.