The attack in North Waziristan came a day after a militant commander said a month-long ceasefire had been called to give time for tribal elders to broker a settlement to end the conflict in the region.

``We can confirm at the moment that a car packed with explosives rammed a checkpost on the BannuMiranshah road,'' Ghafoor Shah, said a government official.

Two intelligence sources said seven troopers were killed in the blast, while a third said six were killed and five wounded. ``It was a white car and only one person, the driver, was in it,'' an Intelligence official said.

Security forces have killed more than 300 militants, including 75 foreigners, in North Waziristan since last year, after the military switched its offensive from South Waziristan.

Several Arab Lieutenants of alQaeda leader Osama bin Laden have been killed in North Waziristan, and US Drone aircraft have carried out missile strikes on al-Qaeda targets from across the border in Afghanistan.

Most of the casualties have occurred since March, when fighting escalated dramatically after militant Muslim clerics called on tribesmen to take up arms following a missile strike by Pakistani helicopters on a large al-Qaeda camp close to the Afghan border.

The approach to the site of the suicide attack, around 300km southwest of Islamabad, was cordoned off.