Updated

An apparent U.S. missile attack destroyed a suspected militant compound in northwestern Pakistan on Tuesday, killing at least nine people, two intelligence officials said.

It was not immediately clear who was targeted in the strike, in the Datta Khel region of North Waziristan, said the officials on condition of anonymity because they were not authorized to talk to the media. An unknown number of people were injured.

The CIA has stepped up missile strikes on militant positions in Pakistan's tribal regions since December, when a suicide bomber killed seven CIA employees in neighboring Afghanistan.

Pakistan publicly criticizes the U.S. missile attacks, saying they violate its sovereignty and fuel more anti-Americanism among the population, but Islamabad is widely believed to be sharing intelligence with the Americans on at least some of the strikes.

Washington refuses to publicly discuss the program, which uses unmanned drones, but Pakistani intelligence and government officials say privately the attacks have killed several senior Al Qaeda and Taliban commanders in recent years.