Pakistan closed the main supply route for Nato forces in Afghanistan yesterday as it launched an offensive backed by tanks and helicopter gunships against Taleban forces in the strategic Khyber Pass.

Troops pounded suspected militant hideouts with heavy artillery, killing several insurgents who had frequently ambushed the convoys, interrupting military supplies in recent weeks.

Security officials imposed a curfew, warned tribesmen against sheltering Islamic militants and said the highway linking Peshawar to the border town of Torkham would remain closed until the operation was completed.

Tariq Hayat Khan, the administrator of the Khyber tribal agency, said: “We want to get rid of them and we mean business this time. Supplies to Nato forces will remain suspended until we clear the area of militants and outlaws who have gone out of control.” The latest offensive came after a series of spectacular attacks by the militants on lorry terminals in the outskirts of Peshawar, which destroyed hundreds of Nato supply vehicles. There has also been a spate of hijackings. Several drivers have been killed, bringing many truckers to stop taking supplies along the route. Heavily armed paramilitary escorts have failed to prevent attacks.

About 75 per cent of the supplies and equipment used by Nato and US-led forces fighting the Taleban in Afghanistan are shipped to the Pakistani port of Karachi, where they begins a treacherous 1,200-mile land journey to Kabul via the Khyber pass.

There is a second route from Karachi through the town of Chaman to the southwest, leading to the Afghan city of Kandahar but that has also come under attack recently.

The ambushes in the Khyber have forced Nato to look for alternatives, including through Central Asia into northern Afghanistan. The supply route is likely to be even more important as the United States increases its troops in Afghanistan, perhaps doubling the number to about 60,000 next year.

Pakistani officials said the situation in the Khyber worsened when Baitullah Mehsud, the head of the Pakistani Taleban movement, whose power base is hundreds of miles to the south in Waziristan, dispatched about 400 tribal fighters to the Khyber region to take on Western convoys along the mountain route. The militants are backed by a network of informants with advance knowledge of the convoys’ freight and timetables.

Until the arrival of insurgents from the south, Khyber was the most peaceful of Pakistan’s seven tribal regions Domestic politics have further complicated matters, however. Last week Jamaat-e-Islami, the most powerful Islamist party in Pakistan, threatened to block roads to Afghanistan if the United States continued its missile strikes against militants in Pakistan.

Faced with worsening security, the United States and the Afghan Government are considering the establishment of a force of unarmed “community guards” in villages beyond the reach of Western troops. The force would be given training, clothing and other supplies, as well as international back-up, so they could respond “with confidence” to insurgents.

William Wood, the US Ambassador in Kabul, insisted: “We do not intend to provide weapons to anyone in this programme. This is not a re-creation of tribal militias.”

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