Security officials in northwest Pakistan say a U.S. drone strike has killed at least four militants in the restive tribal region near the Afghan border.

Officials say the drones fired at least four missiles Saturday, hitting a house in the Degan area of North Waziristan, a known stronghold of al-Qaida and the Taliban.

Authorities say the targeted area is dominated by the Hafiz Gul Bahadur militant group.

Drone strikes are a contentious issue between Washington and Islamabad. Pakistan says the strikes violate its sovereignty, but the United States believes they are an important tool in the effort to defeat al-Qaida.