A U.S. drone strike killed at least four people in North Waziristan tribal region Monday night, a private TV reported. According to the report, the spy aircraft fired four missiles on a compound and a vehicle at Naurak, a small town some 15 kilometers from Miranshah, the center of North Waziristan. On the other hand, Pakistani intelligence officials say US drone-fired missiles have killed four suspected militants close to the Afghan border. The officials say the strike Monday on a vehicle took place close to the town of Mir Ali in the North Waziristan tribal region. The identities of those killed were not known. The officials spoke on condition of anonymity because they were not authorized to brief the media. It was the forth strike in Waziristan tribal region in five days. On Sunday, a U.S. spy aircraft fired six missiles on a house in North Waziristan tribal area and killed at least six people. At least ten people, including two Taliban commanders, were killed in both strikes in South and North Waziristan on Thursday. The United States has stepped up drone strikes in recent days despite strong opposition by the Pakistani government. Pakistan Prime Minister Yusuf Raza Gilani said on Saturday that no permission had been granted to the United States to launch drone attacks on targets inside Pakistan. Gilani, who was in Australia for the Commonwealth Heads of Government Meeting (CHOGM), told a group of Pakistani expatriates that the 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 the drone attacks were one of the reasons why relations between Pakistan and the United States had deteriorated in recent months. 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-Qaida and Taliban militants.