The Pakistani army says it is increasing its presence along the Afghan border to search for Taleban and al-Qaeda fighters still active in the area.

Never before has the army penetrated these remote stretches ruled by tribal custom

General Orakzai, Pakistan army

New checkpoints are being set up and troop patrols intensified in an operation senior officers are calling historic.

It will be the first time that government troops have gone into remote mountainous regions that have traditionally been left to tribal rule.

Two US Afghans, meanwhile, are being questioned in the area after their arrest last week on suspicion of entering Pakistan illegally.

Officials say it is not clear whether the two men, both carrying US passports but no Pakistani visas, have links with Osama Bin Laden's al-Qaeda network.

'Historic first'

Pakistan's tribal areas, set up after partition from India, stretch for hundreds of miles along the border with Afghanistan.

Although strictly speaking part of Pakistan, they have their own laws and customs and the writ of the authorities does not run there.

The Pakistani army says it has established border checkpoints in different parts of the tribal areas in order to intercept Taleban and al-Qaeda suspects.

A statement issued in the provincial capital, Peshawar, said troops had gone into North and South Waziristan, previously considered no-go areas.

Troops had been issued with night-vision surveillance eqipment to allow round-the-clock border patrols, it added.

Corps Commander Lieutenant-General Ali Muhammad Jan Orakzai, visiting the troops, told them they were living through historic times.

He also met local tribal elders and praised them for their assistance, the statement said.

"Never before has the army penetrated these remote stretches ruled by tribal custom," it quoted him telling local leaders.

"Such cooperation from tribal areas... marks a historic first for Pakistan."

Reinforcements

The army has not, however, said how many troops it has deployed on the Afghan border.

Tribal areas have their own laws

And there has been no mention of Monday's reported search operation by US and Afghan troops in Pakistani tribal areas.

Reports in the Western press suggest Pakistan has recently sent another 250 troops to the tribal areas, following US requests.

American officials believe concentrations of al-Qaeda fighters remain in the region.

Pakistan has until now resisted US pressure to launch large-scale search operations in the semi-autonomous border region for fear of provoking tribal opposition.