Al-Qaeda’s No. 2 leader, Abu Yahya al-Libi, the charismatic commander who helped steer the terrorist group after Osama bin Laden’s death last year, was killed by a CIA drone strike in Pakistan’s lawless frontier region, U.S. officials confirmed Tuesday.

U.S. intelligence officials said the death of the Libyan jihadist, who escaped from U.S. custody in Afghanistan in 2005, leaves al-Qaeda’s leadership ranks in Pakistan so depleted that there is no obvious successor.

Libi, the second al-Qaeda deputy commander to be killed in 10 months, was targeted in a drone strike early Monday on a house in North Waziristan, U.S. officials said. Despite reports from Pakistan that more than a dozen people died, U.S. officials said Libi was the only one killed.

A U.S. official described Libi as one of al-Qaeda’s “most experienced and versatile leaders.” His death was viewed as a particularly heavy loss for al-Qaeda because of his standing as both a spiritual figure and operational manager for a terrorist organization that has been struggling since bin Laden’s death at the hands of Navy SEALs last year.

The death of Libi “puts additional pressure on al-Qaeda in the post-bin Laden era,” said White House press secretary Jay Carney. It “damages the group’s morale and cohesion and brings it closer to demise than ever before,” he said.

The missile strike also illustrates the Obama administration’s determination to continue the CIA drone campaign despite escalating Pakistani objections, which were reiterated Tuesday when an American diplomat was summoned to Pakistan’s Foreign Ministry in Islamabad.

U.S. charge d’affaires Richard Hoagland “was informed that the drone strikes were unlawful, against international law and a violation of Pakistan’s sovereignty,” according to a statement from the Islamabad government.

The message was delivered amid a flurry of drone activity in Pakistan, with three strikes since Saturday. U.S. officials said Libi was among a total of three operatives killed.

The pace of the drone campaign reflects the extent to which the CIA has continued to patrol Pakistan with unmanned aircraft, even as the terrorist threat has shifted. U.S. officials now see al-Qaeda’s affiliate in Yemen as significantly more dangerous than the core group in Pakistan, but the number of strikes this year in each country stands about even.

According to the Long War Journal Web site, there have been 22 drone strikes in Yemen and 21 in Pakistan.

Libi’s death “underscores we cannot give in to Pakistan’s demand for an end to drone operations,” said Bruce Riedel, a former CIA analyst who is a counter­terrorism expert at the Brookings Institution.

‘He was an absolutist’

Libi was among a collection of aliases used by a militant whose given name was Muhammad Hasan Qaid, according to the International Institute for Counter-Terrorism.

He was one of the last surviving members of the generation of al-Qaeda fighters who battled against the Soviets in Afghanistan. He was admired among the group’s rank and file and served as a bridge between al-Qaeda’s Pakistan leadership and affiliates around the world. Libi also possessed credentials that allowed him to issue religious edicts and operational mandates to the group’s adherents.

Libi “played a critical role in the group’s planning against the West,” said the U.S. official, who spoke on the condition of anonymity to discuss American counter­terrorism operations. “There is no one who even comes close in terms of replacing the expertise AQ has just lost.”

Libi, thought to be in his late 40s, had moved into the No. 2 spot after the death in August of Atiyah abd al-Rahman, another Libyan national killed in a missile strike. Like his predecessor, Libi was regarded as the group’s general manager, answering to al-Qaeda’s senior commander, Ayman al-Zawahiri.

Libi, a former member of the Libyan Islamic Fighting Group, rose to celebrity within al-Qaeda’s ranks after he escaped in 2005 from the U.S. detention facility at Bagram, Afghanistan.

Jarret Brachman, a government consultant and al-Qaeda expert, said Libi was embittered by his imprisonment and animated by an ideology that was virulently anti-Western and “extreme,” even by al-Qaeda’s standards. “He was off the reservation, ideologically,” Brachman said. “He was an absolutist, at war with the West, at war with the Shia. Yet he knew how to package his views and communicate them in a way that sold.”

Libi is the latest in a series of leaders to be killed within months of ascending to al-Qaeda’s top operational post. The position was considered the group’s No. 3 job before bin Laden’s death.

In a measure of the rapidity of that turnover, Libi was not even listed on public U.S. counterterrorism charts until 2009, when he was added to the Rewards for Justice Web site, which until this week had offered $1 million for information on his whereabouts.

Differing accounts of strike

A senior Pakistani official played down Libi’s importance and said the government in Islamabad had played no role in providing information for the drone strike. The drone program is “unfinished bad business between us,” the official said. “They rarely get anything more than foot soldiers. It’s diminishing returns.”

U.S. and Pakistani officials confirmed that the missile targeting Libi had struck a house in North Waziristan at sunrise Monday. A security official from the area said in a phone interview that numerous “foreigners” were described as being among the victims, and other Pakistani sources put the death toll at 16. U.S. officials disputed those reports, calling them “wildly” inaccurate.

With Libi’s death, al-Qaeda lost not only a seasoned leader but also a key representative to its affiliates abroad, said Seth Jones, a Rand Corp. analyst and author of “Hunting in the Shadows: The Pursuit of al Qa’ida after 9/11.”

Libi “was most directly involved in maintaining relations with the affiliates,” including franchises in North Africa, Jones said. “His death will have an impact on those networks,” Jones said, though he added that al-Qaeda has managed to survive previous losses of key leaders. “No one is irreplaceable,” he said.

Special correspondents Haq Nawaz Khan in Peshawar, Pakistan, and Shaiq Hussain in Islamabad and staff researcher Julie Tate and staff writer David Nakamura in Washington contributed to this report.