MIR ALI, Pakistan » A suspected U.S. drone fired two missiles at a vehicle and a house in a militant stronghold in northwestern Pakistan on Sunday, killing four alleged militants, Pakistani intelligence officials said.

The attack took place in Doga Mada Khel village in North Waziristan, part of Pakistan’s tribal area that is dominated by militants who regularly launch attacks against U.S. troops in Afghanistan, said the officials, speaking on condition of anonymity because they were not authorized to talk to the media.

The identities of the suspected militants killed in the strike were unknown, but the village is controlled by fighters loyal to the powerful militant commander Hafiz Gul Bahadur.

The U.S. has stepped up its use of drone strikes to target militants in North Waziristan given the reluctance of the Pakistani army to launch an offensive in the area.

The army says its troops are stretched too thin carrying out operations in other parts of the tribal region. Many analysts believe Pakistan is reluctant to target militants in the area with whom it has historical ties and could be useful allies in Afghanistan after foreign troops withdraw.

The U.S. refuses to acknowledge the covert CIA drone strikes in Pakistan publicly, but officials have said privately that they have killed senior Taliban and al-Qaida commanders.