© AFP/Getty ImagesAnwar al-Awlaki was implicated in a botched attempt to bomb a Detroit-bound plane at Christmastime in 2009.
Two U.S. officials told Reuters that it was a CIA drone strike that killed al-Awlaki. A source in Yemen told NBC News' Richard Engel that three missed drone attacks targeted al-Awlaki in the past month.
"The terrorist ... has been killed along with some of his companions," the Yemen defense ministry said in a statement sent by text message to journalists earlier Friday, Reuters reported.
The Yemen Defense Ministry also announced Friday that another American in al-Qaida, Samir Khan, was killed with al-Awlaki.
A Yemeni security official told Reuters that al-Awlaki, who is of Yemeni descent, was hit in a Friday morning air raid in the northern al-Jawf province that borders oil giant Saudi Arabia.
He said four others killed with him were suspected al-Qaida members.
NBC News reported that U.S. officials had confirmed that an unmanned American drone had launched the airstrike. A U.S. drone aircraft targeted but missed him in May.
U.S. Rep. Peter King, a Republican who is chairman of the House Committee on Homeland Security, hailed al-Awlaki's death as "a great success in our fight" against al-Qaida and its affiliates in a statement sent to NBC News.
"For the past several years, al-Awlaki has been more dangerous even than Osama bin Laden had been. The killing of al-Awlaki is a tremendous tribute to President Obama and the men and women of our intelligence community," he added.
'We must remain vigilant'
King, however, warned that "we must remain as vigilant as ever, knowing that there are more Islamic terrorists who will gladly step forward to backfill this dangerous killer."
Al-Awlaki was considered such a threat to the U.S. that the Obama administration took the unprecendented step of putting him, an American, on the U.S. military's and CIA's "kill or capture" target list.
U.S. intelligence officials told NBC News that the fact he was an American made him an even more insidious threat.
"As an American he knows how we think, how we react, and how to push all our buttons," one told NBC News.
However, some U.S. military officials were hesitant to confirm al-Awlaki's death, because they have no forces on the ground to positively identify the body, NBC reported. It was wrongly reported that al-Awlaki was killed in an airstrike in December 2009.
Al-Awlaki was implicated in the so-called underwear bombing attempt on a U.S.-bound plane on Christmas Day in 2009.
He was one of the top officials at al-Qaida in the Arabian Peninsula (AQAP), which was also thought to have been behind the plot to send printer cartridges packed with explosives to the U.S.
AQAP usually confirms the deaths of its members or affiliates on Internet posts a few days after the attack.
Propagandist
Al-Awlaki was not the leader of AQAP - that role belonged to Nasser al-Wuhayshi - but he ranked as its most gifted English-language propagandist.
He preached at mosques in northern Virginia and San Diego attended by three of the Sept. 11 hijackers in the 18 months before the attacks.
In 2010, U.S. officials designated him an individual who had committed or was likely to commit a terrorist act and froze his assets.
U.S. officials say he built a substantial following in the United States and other Western nations through English-language postings on the Internet.
But intelligence officials believed that contrary to his public persona, al-Awlaki wasn't the most pious of individuals, a senior Obama administration official told NBC News, as he was said to be dating a Croatian stripper.
Regardless, one of the biggest concerns about al-Awlaki has been his success in attracting and inspiring disaffected young Muslims, some of them converts to Islam.
Major Nidal Malik Hasan, the U.S. Army psychiatrist who is charged with killing 12 people in a shooting spree at the Fort Hood military base in Texas in 2009, was an admirer and emailed the preacher.
A senior Obama administration official said Hasan attended al-Awlaki's sermons in Virginia, and kept in touch with him via email, NBC News reported. After Hasan allegedly carried out the attack, the official said, al-Awlaki praised his "student and brother" on his blog.
Al-Awlaki was also widely attributed as the force behind "Inspire" magazine, a production of AQAP. At the time of its debut, the U.K.'s Guardian newspaper described it as "designed for aspiring jihadis who cannot read Arabic, [offering] tips on bomb-making and encryption for beginners as well as heavyweight Quranic commentary and crude propaganda."
A senior Obama administration official said al-Awlaki "wrote several articles for AQAP's Inspire magazine in order to promote al-Qaida's violent narrative to Westerners and encourage individual action against innocent men, women and children," NBC News reported.
Yemen in turmoil
Yemen has been mired in turmoil as eight months of mass protests demanding an end to President Ali Abdullah Saleh's 33-year rule continue, with international powers fearing that the unrest has emboldened AQAP.
During the unrest, militants with suspected links to the group have seized towns in a southern coastal province near a strategic shipping lane.
One analyst said al-Awlaki's killing would be more of a boon to Saleh than a loss for AQAP.
"For AQAP, these franchises are usually resilient. There are other capable leaders in AQAP who can fill his shoes," said Theodore Karasik, security analyst for the Dubai-based INEGMA group. "It's a short step backwards which will likely result in more assertion in the future, for the revenge of his martyrdom."
Comment: The U.S., as it has been, is able to be Judge, Jury and Executioner of people who are merely Suspects.