Deputy leader of al Qaeda in the Arab Peninsula, Said al-Shehri, a Saudi national identified as Guantanamo prisoner number 372, speaks in a video posted on Islamist websites, in this 2009 file image.
Updated 4:50 p.m. ET: An airstrike by an American drone missile has killed Saeed al-Shihiri, the second in command of al-Qaida in the Arabian Peninsula (AQAP) and five others in Yemen, U.S. officials confirmed on Monday.
The Saudi-born al-Shihiri had been released from the Guantanamo Bay detention facility in 2007. U.S. officials told NBC News that he was also believed to be directly involved in the underwear bomber blot to blow up an airliner over Detroit on Christmas Day in 2009. The bomb failed to blow due to a faulty detonator. Umar Farouk Abdulmutallah was convicted and sentenced to life in prison in the plot.
The airstrike and al-Shihiri's death were first reported by Yemeni officials. Some reports indicated that he was killed by Yemeni forces rather than a U.S. drone.
The United States has used unmanned drones to target AQAP, which has planned attacks on international targets including airliners and is described by Washington as the most dangerous wing of al-Qaida.
Yemen's government is trying to re-establish order after an uprising pushed out veteran ruler Ali Abdullah Saleh in February, but faces threats from Islamist militants, southern secessionists and a Shiite rebel movement in the north.
The protests and factional fighting have allowed al-Qaida's regional wing to seize swathes of south Yemen, and Shiite Muslim Houthi rebels to carve out their own domain in the north.
The lawlessness has alarmed the U.S. and Yemen's much bigger neighbor Saudi Arabia, the top world oil exporter, which view the impoverished state as a new front line in their war on al-Qaida and its affiliates.
Officials have said the attack is likely the work of al-Qaida. The terrorist network has grown in Yemen because the country hasn't had an effective government for an entire year. NBC's Richard Engel reports.
Washington, which has pursued a campaign of assassination by drone and missile against suspected al-Qaida members, backed a military offensive in May to recapture areas of Abyan province.
But militants have struck back with a series of bombings and assassinations.
Reuters and NBC's Mohammed Muslemany in Cairo contributed to this report.
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