Suspected U.S. missiles hit buildings in two Pakistani villages close to the Afghan border, killing about 20 people, most of them alleged militants, officials said Saturday.

The United States has launched a flurry of strikes in recent weeks against suspected Al Qaeda and Taliban targets in northwestern Pakistan, straining ties between the two anti-terror allies.

Pakistan has been unwilling or unable to eliminate militant sanctuaries blamed for rising violence on both sides of the frontier. The region is a possible hiding place for Al Qaeda chief Usama bin Laden.

Two Pakistani intelligence officers said two missiles believed to have been fired from American unmanned drones launched from neighboring Afghanistan hit two villages in the same district of the North Waziristan tribal region just before dusk on Friday.

One attack in Mohammadkhel village, some 28 miles west of Miran Shah, the region's main town, killed about 19 people, most of them alleged militants and including about a half-dozen foreigners, the officials said, citing agents in the field.

The intelligence officials spoke on condition of anonymity because they were not authorized to speak to media on the record.

Pakistan army spokesman Maj. Gen. Athar Abbas also said initial reports indicated that 20 or more people were killed. He said there was "speculation" that many were foreign militants, but cautioned that the army was still awaiting a detailed report.

There were no reported casualties in the other strike in the village of Khata Kaly.

Lt. Nathan Perry, a spokesman for the U.S.-led coalition in Afghanistan, said he had "no information to give" about the reported attacks. He did not deny U.S. involvement.

Friday's attack appeared to be the deadliest of 11 reported cross-border operations by U.S.-led forces since Aug. 20.

U.S. officials have acknowledged some of the strikes. However, they have provided few details, and casualty reports from the dangerous and remote border region are nearly impossible to verify.

Pakistan's military and civilian leaders have complained that the attacks violate the country's sovereignty, kill civilians and anger the local population, making it harder to crack down on the militants.

Militants on the Pakistan side of the border are blamed for a surge in attacks on U.S. and NATO troops in Afghanistan, where violence is running at its highest level since the 2001 U.S.-led invasion toppled the Taliban.

Extremists based in the border region are also blamed for rising attacks within Pakistan, including the Sept. 20 truck bombing of the Marriott Hotel in Islamabad that killed more than 50 people.