The White House on Tuesday described the death of al-Qaida deputy leader Abu Yahya al-Libi as a "major blow" to the militant group and said there was no clear successor to take over his role.

Abu Yahya al-Libi, a veteran militant said to have been a leader of the group´s operations, and who survived previous U.S. attacks, was killed in a U.S. drone strike early Monday morning on a hideout in North Waziristan in Pakistan´s tribal areas, U.S. officials announced on Tuesday.

White House spokesman Jay Carney, citing U.S. intelligence sources, said Libi was al-Qaida´s "general manager" responsible for overseeing day-to-day operations in the tribal areas of Pakistan, and managing relations with affiliates.

"We have confirmation of his death," Carney told a news briefing, declining to say where or how the network´s deputy leader died. "There is now no clear successor to take on the breadth of his responsibilities," he said.

He went on to reaffirm the U.S. president´s commitment to dismantling al-Qaida. "I can´t get into details about al-Libi´s death, the circumstances or the location. You know, I would simply say that this president is firmly committed to carrying out his policy objectives in Afghanistan and in the Afghanistan-Pakistan region, which is to disrupt, dismantle and ultimately defeat al-Qaida," Carney said.

"He is committed to disrupting, dismantling and ultimately defeating al-Qaida beyond that region too. That´s why we cooperate with countries around the world in efforts to counter al-Qaida and other extremists."

But even as al-Qaida´s core group, now led by Ayman al-Zawahri, has faced mounting losses, its affiliates elsewhere - particularly in Yemen - have continued planning attacks on U.S. and other Western targets.

And the drone strikes, which have escalated in number over the last two weeks, have deeply angered Pakistan´s government, contributing to unrelenting tensions between Washington and Islamabad.

Pakistan on Tuesday called in the U.S. charge d´affaires to its foreign ministry to convey "serious concerns" over the drone strikes, a ministry statement said.

For the United States, Libi had been one of al-Qaida´s most dangerous figures. Recently released letters written by Osama bin Laden and captured during the U.S. raid in which he was killed last year show Libi to have been one of a handful of al-Qaida officials relied upon by bin Laden to argue al-Qaida´s case to a worldwide audience of militants, in particular to the young.

Libi, a cleric whose real name was Mohamed Hassan Qaid, escaped from U.S. custody in Afghanistan in 2005 and on at least one previous occasion was prematurely reported to have been killed in a U.S. drone strike.

A Pakistani Taliban leader, speaking to Reuters by telephone from an undisclosed location, said Libi "had been living in the Mirali area for quite a while. Most of the people from his group were also in Mirali. When the first missile hit, they went to the house to check the damage."

"And immediately, another missile hit them at the spot. Unfortunately, Sheikh sahib (Libi) was martyred. This is a big loss, he was a great scholar. After doctor Sahib (Zawahri), he was the main al-Qaida leader," the Pakistani Taliban leader said.

U.S. President Barack Obama has made strikes against anti-U.S. militants, and particularly the killing of bin Laden, a major component of his bid for re-election in November.

Sajjan Gohel, chief executive of the Asia-Pacific Foundation security research consultancy, said Libi was one of the few remaining key figures within al-Qaida´s core.

He "has also been at the center of al-Qaida´s plans to reconstitute itself and try and remount a trans-national terror campaign. This is one of the reasons he was viewed as a high value target," he told Reuters by email.

Still, some analysts say the death of an al-Qaida leader does not necessarily spell disaster for the group, arguing it is decentralized and offers inspiration to militants and not just logistical support or financing.

"Even if he´s killed it doesn´t matter much to the organization as long as Dr Zawahri remains alive," said Imtiaz Gul, author "The Most Dangerous Place", a book about the lawless border area between Pakistan and Afghanistan.

But Jarret Brachman, a terrorism expert who consults for U.S. government agencies, said that in his view, in its recent configuration, the coherence of al-Qaida´s core organization was entirely dependent on two men: Zawahri and Libi, whose activities Brachman says he had tracked closely since 2005.

Brachman said that his view is that Libi´s death is a "cataclysm" for al-Qaida´s core group in terms of their ability to organize and continue to spread their ideology. "There´s nobody left" in the central organization if Zawahri at some point is killed or otherwise taken off the battlefield, Brachman said.

He said that al-Qaida central still had a few operatives who were capable of "blowing people up." But in terms of being able to present a coherent ideology and theology to potential followers, Libi´s death was a major blow to the organization.

"He was their theological pitbull," Brachman said. (© Copyright 2012 Ha´aretz 06/06/12)