Al-Qaida in the Arabian Peninsula, which claimed responsibility for the attempted attack on a U.S. airliner bound for Detroit, is led by a Yemeni who was once a close aide to Osama bin Laden.
The group formed in January this year, when leader Naser Abdel Karim al-Wahishi announced a merger between operatives from Saudi Arabia and Yemen.
Al-Wahishi, who goes by the alias Abu Basir, was among 23 al-Qaida figures who escaped from a Yemeni prison in 2006. He is on Saudi Arabia's most wanted list, which includes many militants currently in Yemen.
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At least two former detainees released in November 2007 from the U.S. military prison in Guantanamo Bay, Cuba, have resurfaced as al-Qaida commanders in Yemen.
Said al-Shihri, who was released from a Saudi rehabilitation program last year, is a deputy leader of the organization in Yemen. Another former Guantanamo inmate, Abu al-Hareth Muhammad al-Oufi, surfaced in January in a video clip showing him sporting a bandolier of bullets as an al-Qaida field commander.
Al-Qaida in the Arabian Peninsula has been blamed for a series of attacks in Yemen, including an assault against the U.S. embassy in San'a, and suicide bombings targeting South Korean visitors.
Recently, the group indicated it was ready to take its fight beyond Yemen. The government there said the Nigerian accused in the Christmas day attack on the U.S. airliner visited Yemen this year.
In claiming responsibility for that attack, al-Qaida urged supporters to get the "infidels" out of the Arabian peninsula. The call echoed Osama bin Laden, who criticized Saudi Arabia for hosting American military bases.
The group's first operation outside Yemen was carried out in Saudi Arabia this August against the kingdom's counterterrorism chief, though that bomb attack failed.
Experts believe the al-Qaida fighters number in the low hundreds. The group appears to be well funded and has found sanctuaries among a number of Yemeni tribes, particularly in three eastern provinces.
Yemen, the ancestral home of bin Laden's family, has been an al-Qaida haven partly because of a weak central government and rugged terrain where it is easy to hide.
The country was the scene of the 2000 suicide bombing of the destroyer USS Cole off the Aden Coast that killed 17 American sailors.
Just before the failed Christmas attack, Yemeni airplanes, backed by U.S. and Saudi intelligence, carried out two air strikes against al-Qaida operatives in eastern Yemen.
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