A U.S. pilotless aircraft fired six missiles on a house in Pakistan's North Waziristan tribal region on Sunday, killing at least 6 people, local media reported.

The Express TV reported that the U.S. pilotless aircraft struck a house and a vehicle at Datta Khel area, just few km from Miranshah, the center of North Waziristan.

It was not clear as to who were targeted in the strike, the third attack in Waziristan tribal region within four days.

Residents in Miranshah said that a U.S. unmanned aircraft had been flying over the area since Sunday morning and launched the strike at around 11:45 a.m. local time. The local tribesmen said that they could not approach the strike site because of fear of another strike.

They said that armed Taliban arrived at the scene and removed the bodies.

It was the third U.S. attack in Waziristan region within four days. At least ten people, including two Taliban commanders, were killed in both strikes in South and North Waziristan on Thursday.

The U.S. has stepped up drone strikes in recent days despite opposition by top Pakistani leaders.

Pakistani Prime Minister Yusuf Raza Gilani said on Saturday in Australia that no permission had been granted to the United States to launch drone attacks on targets inside Pakistan.

"There is no such permission,"Gilani, who is in Australia, for the Commonwealth Heads of Government Meeting (CHOGM), told a group of Pakistani expatriates.

Gilan said that drone attacks were counter-productive because they caused collateral damage and undermined the government's efforts to garner support against extremists and terrorists.

He said that the drone attacks were one of the reasons why relations between Pakistan and the U.S. had deteriorated in recent months.

Pakistani Foreign Minister Hina Rabbani Khar, who is also in Australia, termed the U.S. drone attacks inside its territory as " unjustified" saying these were counterproductive and decreased space for creating support against extremists.

"Our leadership has always condemned these in the strongest terms and unjustified," Hina Rabbani Khar told students at University of Western Australia.

Hundreds of tribesmen staged a rally in Islamabad on Friday and called for immediate halt to the American drone strikes in the tribal regions. They said that innocent people are killed in the strikes.

The U.S. spy aircraft routinely fires missiles in the Pakistani tribal regions, claiming that they target suspected al-Qaeda and Taliban militants.