Unidentified armed men have attacked a Nato supply terminal and a convoy in northwest Pakistan, security forces said.

The attackers struck before dawn on Saturday, setting fire to 11 lorries and 13 containers bound for troops in Afghanistan.

The attack was the fourth in a week on such terminals outside the city of Peshawar, despite an increase in security in the area.

Last weekend, hundreds of lorries were destroyed by fighters armed with rocket launchers, hand grenades and other weapons.

Paramilitary forces are now conducting regular patrols of the area and members of a special anti-terrorist squad have been deployed, Fazal Mahmood, police official, said.

Police say the fighters enter Peshawar from villages in the tribal region of Khyber, which borders Afghanistan, and are well-organised.

A Taliban spokesman told Al Jazeera three weeks ago that attacks would continue "until the [Afghan] government and the Americans are smashed".

"We want to show them they are not all-powerful and the mujahidin of Afghanistan can carry out attacks on our enemies in any part of the country," Zabiullah Mujahid, the spokesman, said.

The route through the Khyber Pass is vital for US and Nato troops fighting the Taliban in Afghanistan. Around 75 per cent of their supplies and equipment are transported through Pakistan.