A U.S. drone strike has killed al-Qaeda's second-in-command, American officials said Tuesday, a significant blow to the  network that has lost a string of top leaders since the death of Osama bin Laden last year.

Abu Yahya al-Libi was considered a media-savvy, charismatic leader who escaped from an American prison in Afghanistan and helped preside over the transformation of al-Qaeda into an extremist movement aimed at winning converts around the world.

White House spokesman Jay Carney called al-Libi's death a "major blow" to the al-Qaeda network.

Carney described al-Libi as an operational leader and a "general manager" of al-Qaeda. He said al-Libi had a range of experience that will be hard for al-Qaeda to replicate and brings the extremist 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-Qaeda since Navy Seals killed bin Laden.  

Al-Libi was killed 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.

$1 million reward

Al-Libi, a hero in militant circles for his 2005 escape from an American military prison in Afghanistan, was elevated to al-Qaeda's No. 2 spot when Ayman al-Zawahri rose to replace bin Laden shortly after he was killed on May 2, 2011.

The U.S. 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.

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.

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This March 25, 2007, file image, made from video posted on a website frequented by Islamist militants, shows al-Qaeda militant Abu Yahya al-Libi, who the U.S. military says was killed in a CIA drone strike on Monday. (File/IntelCenter/Associated Press)

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 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-Qaeda deputy appeared to have been injured 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.

The White House maintains a list of targets to be killed or captured, compiled by the military and the CIA and ultimately approved by the president.

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 protests drone strikes

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 co-operation has come under strain as the relationship between the two countries has deteriorated.

As al-Qaeda'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-Qaeda'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-Qaeda brethren he began appearing in extremist videos.