(CNN) -- Abu Yahya al-Libi, al Qaeda's No. 2 man, was killed in Pakistan on Monday, according to U.S. officials. Al-Libi's death was "another serious blow to core al Qaeda," White House spokesman Jay Carney said. Al-Libi, 49, was a well-regarded figure in jihadist circles and had emerged as one of the terrorist network's most important clerics and propagandists, appearing in countless videos in recent years. He was killed by a CIA drone strike, according to U.S. officials. Drone strikes remain a highly contentious issue between the United States and Pakistan. Who is Abu Yahya al-Libi? By most accounts, al-Libi was effectively al Qaeda's deputy leader.
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Abu Yahya al-Libi, al Qaeda's deputy leader, was killed by a drone strike, U.S. says
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His death was a "very serious blow" to al Qaeda, White House says
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Drone strikes remain highly controversial because of civilian deaths
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"There is no one who even comes close in terms of replacing the expertise [@placeholder] has just lost," said a U.S. official who spoke on the condition of anonymity.