Another official confirmed at least four people were killed in the drone attack, but said the dead had not yet been identified.

Taliban strongholds

More than 45 drone attacks, usually blamed on the US, have been carried out in the region since last August.

Most of the attacks have targeted suspected strongholds of Baitullah Mehsud, the Pakistani Taliban leader, in the neighbouring South Waziristan region.

South Waziristan has become the focus of the Pakistani military's offensive against Taliban sympathisers after it launched an assault in the Swat Valley and Buner in April.

The military has been carrying out bombing runs and firing mortar rounds at Taliban targets in the region as part of efforts to kill or capture Mehsud, who is blamed for organising many of the suicide attacks in Pakistan over the past few years.

But Pakistan has said the suspected US drone attacks damage its campaign by alienating local tribes it is trying to enlist in the fight.