U.S. missiles fired from a drone in a Pakistani tribal region near the Afghan border killed eight suspected militants early Sunday, officials said, as the controversial American strikes continue despite Islamabad's persistent demands that they stop, The AP reports.

The latest attack killed fighters loyal to militant commander Hafiz Gul Bahadur, the officials said. Bahadur is believed by residents of the region to have an informal working relationship with the Pakistani army, refraining from targeting the security forces while focusing on U.S. and NATO forces in nearby Afghanistan.

The continued strikes, despite the likely political fallout, show Washington's confidence in the effectiveness of the drone program against al-Qaida and Taliban fighters who allegedly use Pakistanas a base.

Two Pakistani intelligence officials said four Hellfire missiles were fired at a house used by suspected militants in Dre Nishter village of North Waziristan. All the Pakistani officials spoke on condition of anonymity because they were not authorized to speak to the media.

The officials said some foreign militants belong to the Turkmenistan Islamic Movement were believed to have been killed, along with other local fighters from the Bahadur group. Militants from several central Asian countries have joined Afghans, Arabs, and others in Pakistan.

North Waziristan is one of several tribal areas along the border with Afghanistan that are hubs of militant activity. Bahadur controls most of North Waziristan.

The U.S. rarely talks publicly about the covert CIA-run drone program in Pakistan.

The drone attacks are a source of deep frustration and tension between the U.S. and Pakistan. Islamabad says they violate its sovereignty and also cause civilian casualties.

They complicate efforts to normalize the relationship between Washington and Islamabad, including reopening supply routes through Pakistani territory to NATO and American forces in Afghanistan. Islamabad blocked the routes after American airstrikes accidentally killed 24 Pakistani soldiers in November.

The U.S. in turn criticizes Pakistan for failing to crack down on fighters who stage attacks in Afghanistan.