(Reuters) - A series of drone strikes over the weekend and a confrontation on Monday near the border town of Peshawar between U.S. diplomats and local police added new strains to already tense relations between the United States and Pakistan.
U.S. and Pakistani government sources said Abu Yahya al Libi, a senior Al Qaeda leader who had survived previous drone attacks, was a target of one of the latest strikes, which occurred early on Monday in North Waziristan.
U.S. government sources said they were unable to confirm Abu Yahya had been killed. But officials said he was regarded as a very senior aide to al Qaeda leader Ayman al Zawahiri, and that his death would be a major blow to what remains of the central al Qaeda network founded by the late Osama bin Laden.
Abu Yahya is a Libyan militant who has appeared in al Qaeda promotional video messages and once escaped from a U.S.-run prison in Afghanistan.
According to reports from the region, which American government sources did not contest, U.S.-operated drones launched three attacks in tribal areas along Pakistan's border with Afghanistan between Saturday and Monday.
Reports from Pakistan said nearly 30 people were killed during the sequence of strikes, including four suspected militants on Saturday, ten suspected militants on Sunday, and 15 people in the strike in which Abu Yahya was targeted.
There have been eight U.S. drone strikes on targets in Pakistan since President Barack Obama and Pakistani President Asif Ali Zardari attended a NATO summit in Chicago on May 21.
In a diplomatic rebuff reflecting the troubled state of relations between the two countries, Obama declined to meet separately with Zardari, but spoke to him for a few minutes during a picture-taking session.
Meanwhile, sources close to the Pakistani government said that Pakistani police in the border town of Peshawar had detained three Americans, described as U.S. diplomats, and three Pakistanis. Also seized were two land cruisers and what local authorities claimed were illegal weapons.
A senior police official said the Americans were stopped as they were en route to Peshawar, having attended a meeting in the town of Malakand with the vice chancellor of a local university.
The official said police had confiscated five M4 carbines and four 9mm pistols, along with 20 magazines of ammunition.
The American officials told police they were from the U.S. Consulate in Peshawar. The Pakistanis traveling with them were described as consulate security personnel.
Officials in the region said the U.S. officials were quickly freed; the status of their Pakistani colleagues was not immediately clear.
In Washington, U.S. government sources said they had little information on the incident. Initial indications were that the Americans involved were diplomatic security officers who work for the State Department.
The department's diplomatic security bureau had no immediate comment.
The latest incidents occurred as Pakistani officials stepped up public criticism of U.S. drone attacks. Pakistan's foreign ministry said it "strongly condemns" American drone strikes which it described as "illegal attacks" on Pakistani sovereignty.
The Pakistan government says the CIA drone campaign fuels anti-American sentiment in the country, and is counterproductive because of collateral damage.
U.S. officials, however, say such strikes by the remotely piloted aircraft are highly effective against militants and are an important weapon in this kind of war.
"The United States is conducting, and will continue to conduct, the counter-terrorism operations it needs to protect the U.S. and its interests," said one American official.
"The real threats to Pakistan's sovereignty are the al-Qaeda terrorists who are living within their borders and planning attacks on Pakistan, their neighbors, and the West."
U.S. officials repeatedly have expressed Washington's concerns about Pakistani authorities' reluctance to crack down on militants operating on their territory. They have also complained about alleged collaboration or support provided to militants by Pakistan's principal intelligence agency, the Inter Services Intelligence directorate (ISI).
The drone attack on Monday allegedly targeted a militant hideout in the Hesokhel village of the North Waziristan tribal region. Unmanned drones also struck targets in South Waziristan on Saturday on Sunday.
Reporting By Mark Hosenball in Washington, Michael Georgy in Islamabad, Haji Mujtaba in Miran Shah, Jibran Ahmad in Peshawar. Editing by Warren Strobel and Christopher Wilson