Yemen's defence ministry has reported that Anwar al-Awlaki, a well-known and controversial imam with alleged ties to al-Qaeda, was killed along with four others.
A government statement released to the media on Friday said Awlaki was hunted down by Yemeni forces, but did not elaborate on the circumstances of his death. He was wanted by both the US and Yemen.
"The terrorist Anwar al-Awlaki has been killed along with some of his companions," the statement sent by text message to journalists said.
The 40-year-old US-born Awlaki, a dual Yemeni-American citizen, was a father of five. Among those that were killed with him was the co-editor of al-Qaeda's Inspire magazine, Samir Khan, a US citizen of Pakistani origin.
Khan was a specialist in computer programming and was also wanted by the Yemeni government and the US.
Two vehicles hit
Tribal sources told the AFP news agency that Awlaki was killed early on Friday in an air raid that hit two vehicles travelling through an al-Qaeda stronghold in central Yemen.
Government officials say he was targeted 8km from the town of Khashef in the province of al-Jawf, just 140km from Sanaa, the capital.
Barack Obama said the killing of Awlaki was a "significant milestone in the broader effort to defeat al-Qaeda and its affiliates".
Gregory Johnsen, a Yemen analyst from Princeton University, discusses Anwar al-Awlaki's killing
Speaking in Virginia on Friday, the US president described the killing as a tribute to the US intelligence community.
"Awlaki repeatedly called on individuals in the United States and around the globe to kill innocent men, women and children to advance a murderous agenda," he said.
While holding Awlaki "directly responsible" for the deaths of many Yemeni citizens, Obama cautioned that Al-Qaeda in the Arabian Peninsula (AQAP) was still dangerous although it remained a "weakened" outfit.
A senior White House official had earlier confirmed the death of Awlaki.
The news came amid unrest in the impoverished Arabian Peninsula country, where protesters have staged protests since February demanding the resignation of Ali Abdullah Saleh, the country's president since 1978.
The aircraft that carried out the deadly attack was probably American, according to tribal sources, who said US aircraft had been patrolling the skies over Marib, a central Yemeni province, for the past several days.
The tribal sources also said Awlaki had relocated from the nearby Shabwa region about three weeks ago.
A US drone aircraft targeted but missed Alwaki in May, and the Yemeni defence ministry had previously announced Awlaki's death late last year.
Targeted by drones
On December 24, the Yemeni government said he had been killed in an air attack, only to admit later that he was still alive.
"He has been a target of US drones at least three times," Hakim al-Masmari, editor-in-chief of the Yemeni Post, told Al Jazeera.
"The Yemeni government will face a lot of criticism, especially in the south, for allowing US drones to attack Yemeni civilians. But it will not be a blow to Al-Qaeda in the Arabian Peninsula from any perspective. We don't feel they will suffer, because [Awlaki] did not have any real role in [AQAP]."
US officials said Awlaki spread al-Qaeda's message via a blog, social-media posts and email exchanges.
Theodore Karasik, a Dubai-based Gulf security analyst, comments on Awlaki's killing in Yemen
"Mr Awlaki is a problem," John Brennan, Obama's counterterrorism adviser, said in January 2010.
"He's clearly a part of Al-Qaeda in [the] Arabian Peninsula. He's not just a cleric."
Brennan directly accused Awlaki of having links with Major Nidal Hasan, who is suspected of shooting dead 13 people at Fort Hood military base in Texas in November 2009, and who is set to face trial in a military court on March 5, 2012.
Faisal Shahzad, a Pakistani-American who pleaded guilty to the May 2010 Times Square failed car-bombing attempt, told interrogators he was "inspired'' by Awlaki after making contact over the internet.
Awlaki may also have had contact with Umar Farouk Abdulmutallab, the Nigerian student accused of trying to blow up a Detroit-bound Christmas Day aircraft in 2009, Brennan said.
Obama had accused the AQAP of arming and training Abdulmutallab and said the group was also responsible for the October 2010 parcel bomb plot that originated in Yemen.
Two parcels addressed to Jewish institutions in Chicago - containing the explosive PETN hidden in ink toner cartridges - were found to have been freighted from Sanaa on commercial airlines.
Freeze of assets
In July 2010, Obama's administration placed Awlaki on its list of terrorism supporters, freezing his financial assets and banning any transactions with him.
In a video posted on websites last May by AQAP, Awlaki urged Muslims serving in the US army to follow Hasan's example, and also defended Abdulmutallab.
Ameen al-Himyari, a Yemen analyst and professor at Qatar university, told Al Jazeera "terrorism is a phenomenon that needs to be studied" and that killing ring leaders would not solve the problem.
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"We need to know what the reasons [for terrorism] are. Now we've killed the most wanted person in the world, [but] tomorrow we're going to have the most wanted person in the world. So what's the end? We need to find a solution," he said.
He also said Awlaki's death could make it hard for Saleh to cling to power.
"The regime is going to lose one of its scarecrows," he said. "Now if al-Qaeda is weakened in Yemen, what's he [Saleh] going to say for the West? Support me for what?"
The US and Saudi Arabia, Yemeni's neighbour to the north, have backed Saleh's government to fight al-Qaeda's cells in the country's south. But they have also been urging him to step down under a deal brokered by the six-nation Gulf Co-operation Council (GCC), which offers him as well as his family immunity from prosecution.
Saleh has backed out of the deal on three occasions and has said he will not step down if his former allies-turned-rivals are allowed to run in future elections.