Security officials in northwest Pakistan say a U.S. drone strike has killed at least three suspected militants.

Authorities say the missile strike Saturday happened in Miran Shah, the main town in the North Waziristan tribal region, a known hide-out of Taliban and al-Qaida-linked militants.

Drone strikes have become an increasingly contentious issue between Washington and Islamabad. Relations between the allies plunged into crisis after U.S. air strikes killed 24 Pakistani soldiers in November, resulting in Pakistan shutting its Afghan border to NATO supplies.

Pakistan has demanded the U.S. apologize for the November air strike. Washington has refused.

Pakistan says the missile attacks are counter-productive, violate its sovereignty, kill civilians and fuel anti-U.S. sentiment.