Pakistan has closed the route used to supply foreign forces in Afghanistan as its army tries to crack down on insurgents in the area. The operation began at dawn in the Khyber Pass region.
Pakistan wants to stop attacks against the supply convoys and stamp out kidnappings in the area.
Over recent weeks, several depots in the north west of Pakistan have been attacked, with hundreds of trucks burnt, as militants try to cut off supplies to NATO troops.
As Afghanistan is landlocked, supplies are taken by boat to the Pakistani port of Karachi and then driven up through the country.