Abu Yahya al-Libi was considered a media-savvy, charismatic leader with religious credentials who escaped from an American prison in Afghanistan and was helping preside over the transformation of al-Qaida from a close-knit group into an ideological movement aimed at winning converts -- and potential attackers -- around the world.
White House spokesman Jay Carney called al-Libi's death a "major blow" to the terror network.
Carney described al-Libi as an operational leader and a "general manager" of al-Qaida. He said al-Libi had a range of experience that will be hard for al-Qaida to replicate and brings the terror network closer to its ultimate demise than ever before.
Al-Libi was the latest in the dozen-plus senior commanders removed in the clandestine U.S. war against al-Qaida since Navy SEALs killed bin Laden.
A hero in militant circles for his 2005 escape from an American military prison in Afghanistan, al-Libi was elevated to al-Qaida's No. 2 spot when Ayman al-Zawahri rose to replace bin Laden shortly after the terror leader was killed on May 2, 2011.
Carney would not confirm how he was killed, but an American official, speaking on condition of anonymity to discuss intelligence matters, said it was in a drone strike Monday morning. Pakistani officials had previously said that eight militants died in a drone strike in the Pakistani village of Khassu Khel in the North Waziristan tribal area.
Militants and residents in the area told Pakistani agents that al-Libi was in the house when it was hit, Pakistani intelligence officials said. They said the mud and brick house was destroyed in the attack. A vehicle used by al-Libi was destroyed during the strike, said one of the officials.
A local Taliban chief said earlier Monday that al-Libi was not present at the house, though his guard and driver were killed in the attack.
The intelligence officials also declined to be identified because they were not authorized to talk to the media. The Taliban chief spoke on condition of anonymity for fear of being targeted by the Pakistani army.
The White House maintains a list of terrorist targets to be killed or captured, compiled by the military and the CIA and ultimately approved by the president.
The State Department's Rewards for Justice program had set a $1 million reward for information leading to al-Libi, who had filmed numerous propaganda videos urging attacks on U.S. targets.
The U.S. has carried out a flurry of drone strikes recently -- seven in less than two weeks -- some of which appear to have been trying to target al-Libi. The al-Qaida deputy appeared to have been wounded in one of those strikes, although there were conflicting accounts as to which.
Pakistani intelligence officials said al-Libi had been slightly injured in a May 28 attack in a village near Khassu Khel, where he then moved. The Taliban chief said the strike that wounded al-Libi was two days earlier in a different village.
As al-Qaida's de facto general manager, al-Libi was responsible for running the group's day-to-day operations in Pakistan's tribal areas and managed outreach to al-Qaida's regional affiliates.
Al-Libi, an Islamic scholar, was captured in 2002 and held by U.S. forces at the Bagram Air Base in Afghanistan until he escaped in 2005 in an embarrassing security breach. Almost immediately after reuniting with his Taliban and al-Qaida brethren he began appearing in videos released by the terror group.
The Rewards for Justice program described al-Libi as using his "religious training to influence people and legitimize the actions of al-Qaida."
In a 2009 profile of al-Libi in Foreign Policy magazine, terrorism expert Jarret Brachman described al-Libi as "media-savvy, ideologically extreme, and masterful at justifying savage acts of terrorism with esoteric religious arguments."
Al-Libi was one of thousands of men from around the Muslim and Arab world who flocked to Afghanistan in the 1980s to battle the Soviet Union. According to Brachman, he later went to Mauritania for advanced religious studies that he then used in repeated videos and other al-Qaida outreach designed to attract followers and justify the group's deadly tactics. He honed his outreach skills while working in Karachi as webmaster for a Taliban website, Brachman said.
The stepping up of drone strikes since late May follows a relative lull driven by tensions between Washington and Islamabad over American airstrikes last year that killed 24 Pakistani soldiers.
Pakistan seized the opportunity to renegotiate its relationship with the U.S. and demanded Washington stop drone strikes in the country -- a demand the U.S. has ignored. The attacks are unpopular in Pakistan because many people believe they mostly kill civilians, an allegation disputed by the U.S.
Pakistan called Deputy U.S. Ambassador Richard Hoagland to the Foreign Ministry on Tuesday to protest the drone strikes.
"He was informed that the drone strikes were unlawful, against international law and a violation of Pakistan's sovereignty," the Foreign Ministry said in a statement.
Members of the Pakistani government and military have supported the strikes in the past, but that cooperation has come under strain as the relationship between the two countries has deteriorated.
Dozier reported from Washington. Rasool Dawar in Peshawar, Pakistan, Ishtiaq Mahsud in Dera Ismail Khan, Julie Pace in Washington and Sebastian Abbot in Kabul, Afghanistan contributed to this report.