SANA, Yemen In a significant and dramatic strike in the campaign against Al Qaeda, the Defense Ministry here said American-born preacher Anwar al-Awlaki, a leading figure in the groups outpost in Yemen, was killed on Friday morning. In Washington a senior official said Mr. Awlaki had been killed in an American attack by an unpiloted drone firing a Hellfire missile. Mr. Awlakis Internet lectures and sermons have been linked to more than a dozen terrorist investigations in the United States, Britain and Canada. Maj. Nidal Malik Hasan had exchanged e-mails with Mr. Awlaki before the deadly shooting rampage on Fort Hood, Texas, in 2009. Faisal Shahzad, who tried to set off a car bomb in Times Square in May, 2010, cited Mr. Awlaki as an inspiration.
A Defense Ministry statement said that a number of Mr. Awlakis bodyguards were also killed.
A high-ranking Yemeni security official who spoke on condition of anonymity said that Mr. Awlaki was killed while traveling between Marib and al-Jawf provinces in northern Yemen areas known for having an Al Qaeda presence, where there is very little central government control. The official did not say how he was killed.
A senior administration official in Washington said the killing of Mr. Awlaki was important both because he had become Al Qaedas greatest English-language propagandist, and also because he had emerged as one of its top operational planners.
First and foremost, weve been looking at his important operational role, the senior administration official said. To the extent hes no longer playing that role its all to the good.
President Obamas top national security and counterterrorism officials held a video-teleconference at 6:30 a.m. Washington time to discuss details of Mr. Awlakis death as well as its impact on the Al Qaeda affiliate in Yemen and the groups broader organization.
Mr. Awlakis name has been associated with many plots in the United States and elsewhere after individuals planning violence were drawn to his engaging lectures broadcast over the Internet.
Those individuals included Major Hasan, the Army psychiatrist charged in the shootings at Fort Hood in which 13 people were killed; the young men who planned to attack Fort Dix, N.J.; and a 21-year-old British student who told the police she stabbed a member of Parliament after watching 100 hours of Awlaki videos.
But his death could also play into the tangled politics of Yemen, where beleaguered President Ali Abdullah Saleh has been resisting months of protests against his 30-year rule, arguing in part that he is a critical American ally in the war against Al Qaeda.
In early September the Obama administrations top counterterrorism adviser, John O. Brennan, said recent cooperation with Yemen was better than it has ever been despite the prolonged absence of Mr. Saleh, who spent four months in Saudi Arabia after a June bomb attack on his presidential palace.
President Salehs family controls the armed forces responsible for counterterrorism, and the killing of Mr. Awlaki seemed likely to be used to further the argument that the current government is the best ally for the United States when it comes to combating the affiliate group, Al Qaeda in the Arabian Peninsula.
Awlaki may not matter much to Yemenis, but his presence in Yemen has influenced U.S. counter terrorism policy, which in turn has influenced transition politics, said Ginny Hill, the head of the Yemen Forum at Chatham House in London.A senior American military official in Washington said Mr. Awlakis death will send an important message to the surviving leaders and foot soldiers in Al Qaeda, both in Yemen and elsewhere. Its critically important, the senior U.S. military official said. It sets a sense of doom for the rest of them. Getting Awlaki, given his tight operational security, increases the sense of fear. Its hard for them to attack when theyre trying to protect their own back side.
You take out someone like this, it sends a message, the military official continued. Now they have to go into a succession effort that will cause a movement of people, of messages, which makes them more vulnerable. Bottom line, theyve taken a severe impact.
Earlier this year, the American military renewed its campaign of airstrikes in Yemen, using drone aircraft and fighter jets to attack Qaeda militants. One of the attacks was aimed at Mr. Awlaki. Defense Secretary Leon E. Panetta said in July that two of his top goals were to remove Ayman al-Zawahri, Al Qaedas new leader after the death of Osama Bin Laden in May, and Mr. Awlaki.
Word of the killing came after months of sustained American efforts to seriously weaken the terrorist group.
In August an American official said a drone strike killed Atiyah Abd al-Rahman, a Libyan who in the last year had taken over as Al Qaedas top operational planner after Bin Laden was killed.
In July, Mr. Panetta said during a visit to Kabul, Afghanistan that the United States was within reach of strategically defeating Al Qaeda and that the American focus had narrowed to capturing or killing 10 to 20 crucial leaders of the terrorist group in Pakistan, Somalia and Yemen.
A month earlier, an American official said the Central Intelligence Agency was building a secret air base in the Middle East to serve as a launching pad for strikes in Yemen using armed drones.
The construction of the base was seen at the time a sign that the Obama administration was planning an extended war in Yemen against an affiliate of Al Qaeda, called Al Qaeda in the Arabian Peninsula, which has repeatedly tried to carry out terrorist plots against the United States.
The American official would not disclose the country where the C.I.A. base was being built, but the official said that it would most likely be completed by the end of the year.
Last year, the leader of Al Qaedas affiliate in Yemen sought to install Mr. Awlaki as the leader of the group in Yemen, which apparently thought Mr. Awlakis knowledge of the United States and his status as an Internet celebrity might help the groups operations and fund-raising efforts.
Mr. Awlaki, who came form a prestigious Yemeni family, was accused of having connections to the Nigerian Umar Farouk Abdulmutallab, a former engineering student at University College London, who is awaiting trial in the United States for his attempt to detonate explosives sewn into his underwear aboard Northwest Airlines Flight 253 as it landed in Detroit on Dec. 25, 2009. The bomb did not explode.
Mr. Awlaki has been linked to numerous plots against the United States, including the botched underwear bombing. He has taken to the Internet with stirring battle cries directed at young American Muslims. Many of your scholars, Mr. Awlaki warned last year, are standing between you and your duty of jihad.
In Yemen, there was a muted reaction to the news of the death of Mr. Awlaki, who derived his importance from his ability to reach out to the Western, English-speaking world, and held very little importance to the Yemeni population.
Many saw the killing as confirmation of their belief that the United States becomes involved in Yemen only for counterterrorism. Mr. Awlakis death comes at a time when Yemenis protesters, who have been demonstrating against their government relatively peacefully for eight months, are angry at the United States for not doing more to push President Saleh out of office.
Further, if it emerged that Mr. Awlaki was killed by a American drone strike, it will likely further harm the image of the United States among average Yemenis, who are staunchly against outside military intervention in their country.
Laura Kasinof reported from Sana, Yemen, and Alan Cowell from London. Eric Schmitt and Mark Mazzetti contributed reporting from Washington.
This article has been revised to reflect the following correction:
Correction: September 30, 2011
An earlier version of this article said that Yemeni forces had carried out the attack. The circumstances of the operation remain unclear.