Orakzai is the only district in Pakistan's troubled tribal region which does not share a border with neighbouring Afghanistan.

In the neighbouring Khyber tribal district, 24 Islamist militants died when gunship helicopters pounded their positions.

'Security forces also destroyed two militant headquarters, two hideouts and two vehicles,' said a statement from the paramilitary Frontier Corps.

Four paramilitary soldiers were also injured in what was believed to be a hand grenade attack in the same area.

Security forces launched an offensive against Islamist insurgents in Khyber last week, killing more than 150 rebels and arresting nearly 130 in continued fighting. Two dozen militant hideouts and scores of houses were also destroyed.

Khyber serves as the key land route to haul fuel and military equipment for NATO forces fighting the Taliban in landlocked Afghanistan. Militants regularly attack the NATO-bound trucks, temporarily suspending the supplies.