The shadowy Baluchistan Liberation Army said it would strike the oil and gas installation at Dhodak in the central province of Punjab.

It marks an apparent attempt by the group to spread violence beyond the southwestern province of Baluchistan -- where it was blamed for an attack on a gas plant last month which killed eight people -- into other areas.

"We will blow up the oil and gas field in Dhodak if non-locals working at the plant are not expelled," said the group's purported spokesman Azad Baluch -- an apparent nom de guerre meaning Free Baluchistan.

He gave the warning in a telephone call to local newspaper offices Sunday at the same time as claiming responsibility for a bomb which ruptured a gas pipeline, also in Punjab.

The blast on Saturday near Mangrotha in Dera Ghazi Khan district, 90 kilometres (56 miles) west of the central city of Multan, disrupted gas supplies to some places in the populous Punjab.

Local officials said they had taken steps to protect national assets including the Pakistan Atomic Energy Commission facility at Dera Ghazi Khan, some 112 kilometers east of Dhodak.

"We have made all necessary arrangements for the security of sensitive areas like Dhodak gas field, atomic energy station, bridges and railway track in Dera Ghazi Khan district," district police chief Salman Chaudhry told AFP.

He said police and paramilitary troops patrolling in the area were "keeping a vigilant eye on suspects."

"We take notice of all threats or warnings given by terrorists and we are taking the Baluchistan Liberation Army's threat seriously."

Meanwhile a blast Monday blew up a telephone system in a remote town in Barkhan district near the Punjab border, officials said.

"The telephone system of the whole Barkhan district was destroyed when some unknown persons blew up the main transmission tower," Pakistan Telecommunications Corporation spokesman Mahboob Baloch told AFP.

There were no casualties but all four of the district's telephone exchanges were jammed, he said.

BLA spokesman Azad Baluch also claimed responsibility for the blast. "Our activists blew up the tower with explosives," he said in a phone call from unknown place to an AFP reporter in the provincial capital Quetta.

Bombs targetting railway tracks -- including the main line to Iran -- or government installations have been exploding almost daily in Baluchistan, the biggest and poorest of Pakistan's four provinces.

Tribesmen have been waging a rebellion demanding jobs and a bigger share in the profit from Baluchistan's natural resources.

strs-dk-sz/mtp