The unmanned aircraft fired missiles in mountainous Spalga village.

"US drones fired six missiles targeting a militant vehicle and a nearby rebel compound owned by a Tehreek-e-Taliban Pakistan (TTP) leader, Rahimullah, killing six militants," a senior security official in Miranshah told AFP.

Five militants were also wounded in the attack, said the official. The identities of those killed and injured were not immediately known.

Another security official also confirmed the strike and casualties but said it was not clear how many drones had taken part in the attack. He added that several drones were still flying in the area.

Earlier in the day, a US missile strike in the tribal region of South Waziristan had missed its target -- a militant vehicle -- allowing at least four militants to flee.