The missiles struck the vehicle in Mubarak Shahi village, 20 kilometres (12 miles) east of Miranshah, the main town in the North Waziristan tribal district, a stronghold of Taliban and Al-Qaeda-linked militants.

"A US drone fired two missiles at a vehicle when it was transporting militants from one place to another. At least four militants have been killed," a security official in Miranshah told AFP.

Another security official in Peshawar confirmed the attack and casualties. Both officials said the identity of those killed was not yet known.