"The militants first fired and then set ablaze two oil tankers and four trucks loaded with military vehicles," a guard at the depot who declined to be identified said.

Logistical difficulties

The incident conveys the difficulty of undertaking a war in a landlocked nation such as Afghanistan. About 75 per cent of supplies for the Afghan war are sent either through or over Pakistan, including 40 per cent of fuel for troops.

Supplies have become a focus of attack for fighters who aim to stem the resources available to Nato and US forces in Afghanistan.

Supplies along the Khyber Pass have regularly come under attack, forcing the US to find alternative supply routes.

Pakistani forces launched an offensive in early September in the Khyber region against assailants, which they have said has led to the deaths of 175 opposition fighters.

The Khyber Pass is the mountainous border crossing between Pakistan and Afghanistan, nortorious for its tercherous terrain and often lawless outlying regions.