It was the second drone strike in less than two days that took place close to Miranshah, the main town of the North Waziristan tribal region.

"US drones fired four missiles targeting a rebels' vehicle and killing four militants," a local security official told AFP on condition of anonymity because he was not authorised to speak to media.

Another security official also confirmed the strike and casualties.

He said the identities of those killed were not immediately known.