US missiles killed five militants in Pakistan's tribal region Monday, security officials said, a day after six others died as the covert drone campaign in the Taliban-hit region escalates.

Two security officials said a drone fired two missiles on a vehicle in Khaisore village, 25 kilometres (15 miles) east of Miranshah, the main town in militant-troubled North Waziristan.

"Two missiles were fired on a vehicle and at least five militants were killed," a senior Pakistani security official told AFP on condition of anonymity.

The drone strike and the casualties were also confirmed by a local intelligence official.

On Sunday another drone strike 10 kilometres (five miles) away slammed into a militant compound and nearby vehicle and killed at least six militants, officials said.

Washington has dramatically escalated its drone campaign against militants in areas near the Afghan border over the past two months, and argues they are highly effective in the war against al-Qaeda and its Islamist allies.

More than 250 people have been killed in 47 strikes since September 3, angering the government, which is facing criticism for acquiescing to the attacks and reprisals from militant groups based in the area.

The US strikes are deeply unpopular among the Pakistani public, who see military action on Pakistani soil as a breach of national sovereignty and say some attacks have killed innocent civilians.

Pakistan's foreign ministry on Saturday said it would reject any overtures seeking to allow the drone campaign to be expanded outside the tribal areas.

The Washington Post reported Friday that the US was seeking to expand the areas inside Pakistan where Central Intelligence Agency (CIA) unmanned aircraft -- used for surveillance and to launch missile strikes -- could operate.

Washington says the strikes have killed a number of high-value targets, including the former Pakistani Taliban chief Baitullah Mehsud.

The US considers Pakistan's tribal belt an Al-Qaeda headquarters and the most dangerous place on Earth, and has reportedly criticised Pakistan's failure so far to launch a major ground offensive in the tribal region of North Waziristan.