Yemen's defence ministry said on Friday that Anwar al-Awlaki, a US born Muslim preacher linked to al Qaeda's Yemen-based wing, had been killed, in what a security official said was an air strike.
Awlaki had been implicated in a botched attempt by al Qaeda in the Arabian Peninsula (AQAP) to bomb a US-bound plane in 2009 and had contacts with a US Army psychiatrist who killed 13 people at a US military base the same year.
US authorities have branded him a "global terrorist" but Sanaa had previously appeared reluctant to act against him.
It was not immediately clear if Awlaki had been killed in a Yemeni air raid or a US drone strike. A US drone aircraft targeted but missed him in May.
Yemeni officials had previously reported that Awlaki had been killed in late 2009.
Here is some background about Awlaki:
--Born in New Mexico in the United States in 1971, Awlaki is a US citizen. He graduated in civil engineering from Colorado State University and holds a master's degree in educational leadership from San Diego State University.
--Awlaki's family is well-known in Yemen. His father is a former agriculture minister, Nasser al-Awlaki.
--Awlaki is a former imam of mosques in Denver, San Diego and Falls Church, Virginia. Two of those mosques were attended by some of the September 11, 2001, hijackers.
--He travelled to Yemen in 2004, where he taught at a university before he was arrested and imprisoned in 2006 for suspected links to al Qaeda and involvement in attacks.
--He was released in December 2007 because he said he had repented, a Yemeni security official said. But he was later charged again on similar counts and went into hiding.
--Last year the US administration authorised operations to capture or kill Awlaki. "Awlaki is a proven threat," said a US official at the time. "He's being targeted."
Links to AQAP
--Intelligence agencies had viewed Awlaki as chiefly an al Qaeda sympathizer and recruiter for Islamist causes with possible ties to some of the Sept 11, 2001, hijackers.
--That assessment changed in late 2009 with revelations about his contacts with a Nigerian suspect in the attempted bombing of an airliner approaching Detroit on Dec 25, claimed by AQAP, and with a US Army psychiatrist accused of shooting dead 13 people at Fort Hood military base in Texas on Nov 5.
--After the Christmas Day airliner plot, US and Yemeni officials said they learned that Awlaki had met the would-be bomber, Umar Farouk Abdulmutallab.
--Major Nidal Malik Hasan, the Army psychiatrist, had sent emails to Awlaki, which were intercepted by US intelligence agencies and examined by US joint terrorism task forces.
--Hassan was "a hero," Awlaki wrote in a blog post after the attack. "He is a man of conscience who could not bear living the contradiction of being a Muslim and serving in an army that is fighting against his own people," he wrote. Awlaki's website was closed down after the Fort Hood killings.
Importance to AQAP
--Internet-savvy and eloquent in English and Arabic, Awlaki encouraged attacks on the United States and was seen as a man who could draw in more al Qaeda recruits from Western countries.
--Britain's intelligence chief John Sawers singled out Awlaki as a major threat in a speech last October, saying: "From his remote base in Yemen, al Qaeda leader and US national Anwar al-Awlaki broadcasts propaganda and terrorist instruction in fluent English, over the Internet."
--Awlaki is not a very senior Islamic cleric. Nor is he the leader of AQAP -- that is Nasser al-Wuhayshi -- but he ranks as the group's most gifted English-language propagandist.