Pakistani army helicopters attacked militants along the Khyber Pass today while tanks moved in to secure the vital supply link for Western forces in land-locked Afghanistan.
Authorities suspended the shipment of supplies up to the Afghan border yesterday, to clear the way for the military to launch an offensive aimed at ending surging militant attacks on the route.
The Khyber Pass runs between the north-western city of Peshawar and the border town of Torkham and is a vital supply line for more than 65,000 Western troops battling the Taliban insurgency in Afghanistan.
The US military sends 75 per cent of supplies for the Afghan war through or over Pakistan, including 40 per cent of the fuel for its troops, the US Defence Department says.
A second overland route is through the town of Chaman to the southwest leading to the Afghan city of Kandahar, and is likely to become more important as the United States begins moving up to 30,000 new troops into Afghanistan next year.
Militants in Khyber have been trying to choke off supplies for months and have destroyed hundreds of trucks and killed several drivers.
Many truckers have stopped working on the road and supplies had been disrupted but not cut off until authorities sealed the route temporarily on Tuesday.
A spokesman for NATO's Afghan force welcomed the effort to make the route safer and played down the impact on military operations saying the force had stocks.
Nevertheless, the attacks have exposed the vulnerability of the route and forced the alliance to look for alternatives, including through Central Asia into northern Afghanistan.
Pakistani authorities have not said how long the pass will be sealed, only saying they are determined to clear out the militants.
The offensive has coincided with growing tension with old rival India after the late November militant attacks in the Indian city of Mumbai that India blamed on Pakistan-based militants.
The Pakistani military has moved some troops off its western border with Afghanistan in response to the tension.
Reuters