A US drone strike killed at least four suspected militants in Pakistan's restive tribal belt on Wednesday, security officials said.

The unmanned aircraft hit a compound in Kund Sar village, some 60 kilometres (40 miles) south of Miranshah, the main town of North Waziristan tribal region, which borders Afghanistan.

"The drone fired two missiles, killing four people and injuring at least two," a security official in the area told AFP via phone.

"There can be more dead bodies under the rubble," he said, suggesting that the death toll may rise.

An intelligence official in the area confirmed the attack and said that militants loyal to the warlord Gul Bahadur and the feared Haqqani network operate in the area.

Another security official in Peshawar also confirmed the strike and that the Haqqani network and foreign militants are active in the area.

North Waziristan is one of the seven lawless tribal districts of Pakistan that border Afghanistan and has long been a hub for Al-Qaeda and Taliban militants.

The area is off-limits to journalists, making it impossible to independently verify the number and identity of the dead.

Washington pressed Islamabad for years to wipe out the sanctuaries in the North Waziristan tribal area, which militants have used to launch attacks on NATO forces in Afghanistan.

The Pakistani military launched a major offensive in North Waziristan in June and say they have killed more than 1,500 militants so far, with 125 soldiers losing their lives in the operation.