Osama bin Laden, the long-hunted al-Qaeda leader and chief architect of the Sept. 11, 2001, terrorist attacks on the United States, was killed by U.S. forces Sunday in what officials described as a surgical raid on his luxury hideout in Pakistan.

In a rare Sunday night address from the East Room of the White House, President Obama said a small team of U.S. personnel attacked a compound Sunday in Pakistan’s Abbottabad Valley, where bin Laden had been hiding since at least last summer. During a firefight, the U.S. team killed bin Laden, 54, and took custody of his body in what Obama called “the most significant achievement to date in our nation’s effort to defeat al-Qaeda.”

The killing of the terrorism mastermind who had eluded U.S. forces for nearly a decade drew a spontaneous, cheering crowd outside the White House gates and at New York’s Ground Zero, the site of al-Qaeda’s 2001 attacks on the World Trade Center.

“We will be relentless in defense of our citizens and our friends and allies,” a somber Obama said in his nine-minute statement that aired live on television worldwide. “We will be true to the values that make us who we are. And on nights like this one, we can say to families who have lost loved ones to al-Qaeda’s terror: Justice has been done.”

Bin Laden’s killing will provide a clear moment of victory for Obama at a time of deep political turmoil overseas that is upending long-standing U.S. policy in much of the Muslim world, particularly the Middle East.

It also comes nearly 10 years after bin Laden orchestrated the deadliest terrorist attack on U.S. soil, when al-Qaeda terrorists hijacked three passenger jets and crashed them into the World Trade Center and the Pentagon and crashed a fourth jet in rural Shanksville, Pa.

“Today’s achievement is a testament to the greatness of our country and the determination of the American people,” Obama said. “The cause of securing our country is not complete, but tonight we are once again reminded that America can do whatever it is we set our mind to. That is the story of our history.”

The discovery that bin Laden had been hiding in a well-populated part of Pakistan, rather than a remote location, raised new questions about the extent to which Pakistan is cooperating with the United States in combating terrorism.

U.S. forces flew to bin Laden’s hideout in helicopters about 1 a.m. Monday (late Sunday afternoon in Washington). Bin Laden was shot in the head after he and his guards resisted the U.S. attackers, the Associated Press reported. U.S. personnel identified him by facial recognition.

A U.S. official said bin Laden’s body was quickly transported away from Pakistan and “buried at sea,” in part because the U.S. government did not want an accessible gravesite that could become a shrine to bin Laden’s followers. The official declined to identify which body of water the corpse was taken to, or provide further details on how it was transported or handled.

The official said the body was buried “in accordance with Islamic tradition,” meaning within 24 hours of bin Laden’s death. No information was available as to whether Muslim prayers were recited or the body was ritually washed, as is usually required by Islamic law. In general, burial at sea means tipping the body overboard — wrapped, likely, in a shroud — after a brief service.

Obama said neither Americans nor civilians were harmed in the raid on bin Laden’s compound. Three other adult males were killed — two were bin Laden’s couriers and a third was his adult son — according to a senior administration official. One woman was killed when she was “used as a shield by a male combatant” and two others were injured, the official said. There were also children at the compound.

During the raid, which lasted less than 40 minutes, one U.S. helicopter broke down. The crew destroyed the helicopter with explosives, so as not to leave the technology behind, and U.S. forces exited on the remaining aircraft.

“All non-combatants were moved safely away from the compound before the detonation” of the helicopter, a U.S. official said.

U.S. government facilities around the world were placed on heightened alert after the raid, while the State Department issued a worldwide travel alert warning of “enhanced potential for anti-American violence given recent counter-terrorism activity in Pakistan.”

CIA director Leon E. Panetta told his agency that terror groups around the world “almost certainly will attempt to avenge” bin Laden’s death.

“We must — and will — remain vigilant and resolute,” Panetta wrote in a congratulatory memo. “But we have struck a heavy blow against the enemy. The only leader they have ever known, whose hateful vision gave rise to their atrocities, is no more. The supposedly uncatchable one has been caught and killed.”

Years in the making

The secret operation that culminated with bin Laden’s death was years in the making. For most of the past decade, bin Laden was thought to be hiding in Pakistan, but American intelligence had lost his trail until picking up fresh intelligence of his possible whereabouts last August.

After months of studying intelligence and reviewing operational plans, Obama gave the order on Friday morning for the action that ended in bin Laden’s death. The operation took place in Abbottabad, a city of about 100,000 in Pakistan’s Khyber Pakhtunkhwa province, about 65 miles north of Islamabad. Named for a British military officer who founded it as a military cantonment and summer retreat, it is the headquarters of a brigade of the Pakistan army’s 2nd Division.

A Special Operations team conducted the mission based on CIA intelligence, some of which was obtained from detainees in U.S. custody, according to senior U.S. officials who detailed the operation under the condition of anonymity.

“We’ve been staring at the compound for months trying to figure out for sure whether we had enough to go with,” one official said. Operatives have “been working this target for years, years, years. They finally found the guy who led to the guy who led to the guy who led to the guy, and this is it.”

Beginning in September, the CIA began to work with Obama on a set of intelligence assessments, which led him to believe that it was possible that bin Laden might be located at the compound.

By mid-February, Obama determined that there was a sound intelligence basis for pursuing this theory and developing courses of action in case it proved correct. He held five National Security meetings in the second half of March to discuss potential action.

On Friday, shortly before flying to Alabama to visit tornado-ravaged communities, Obama gathered senior officials in the Diplomatic Room. At 8:20 a.m., he made the decision to undertake the operation.

National security adviser Thomas E. Donilon prepared the formal orders and convened senior national security officials that afternoon to plan for the operation. The United States did not share any intelligence with foreign governments, including Pakistan’s, and only a “very small number” of people within the U.S. government knew about it, one official said.

Throughout the afternoon Sunday, Obama met with senior officials in the Situation Room for briefings on the operation. At 3:50 p.m., Obama learned that bin Laden was tentatively identified, and the president remained “actively involved in all facets of the operation, ” a senior administration official said.

The courier

The operation hinged almost entirely on the hunt for a single man: a courier working out of Pakistan who had been trusted by bin Laden for years.

U.S. analysts and operatives spent years figuring out the courier’s identity, senior administration officials said, concluding that he was a former protege of Khalid Sheik Mohammed, the self-declared mastermind of the Sept. 11 attacks who is being held at Guantanamo Bay, Cuba. The courier “had our constant attention,” one official said.

Detainees “identified this man as one of the few al-Qaeda couriers trusted by bin Laden, [and] indicated he might be living with or protecting bin Laden,” the official said. But until four years ago, the United States was unable to track the courier down or uncover his real name. In 2009, U.S. officials narrowed down the region in Pakistan where the courier was working, senior administration officials said.

Then, in August, U.S. officials found the compound that turned out to be bin Laden’s hiding spot. It was described as an extraordinary place, with 12- to 18-foot security walls, multiple interior walls dividing the property and massive privacy walls blocking even a third-story balcony.

“When we saw the compound ... we were shocked by what we saw,” the official told reporters, describing it as “an extraordinarily unique compound,” built perhaps in 2005 and expressly for bin Laden. “Everything we saw ... was perfectly consistent with what our experts expected bin Laden’s hideout to look like.”

A senior official said the property, valued at $1 million, had no Internet or phone service. But photos of the property appeared to show a satellite dish at the property — a discrepancy that was not immediately explained.

Bin Laden’s capture offered a sense of closure for families of those lost in the 2001 attacks. Basmattie Bishundat, whose son, Kris Romeo Bishundat, died at the Pentagon on Sept. 11, was glued to her television in the Maryland suburb Waldorf in the early hours of Monday, wishing she could join the revelers at the White House.

“I cannot believe it, finally,” Bishundat murmured as she watched the pictures from the White House on CNN. “All kinds of emotions. Finally, a sense of closure. Finally, they’ve got the person who started all of this mess.”

With the 10th anniversary of the Sept. 11 attacks approaching this year, bin Laden’s assassination could benefit Obama domestically even more than the capture of former Iraqi dictator Saddam Hussein helped propel then-President George W. Bush to reelection in 2004.

Obama called Bush and former president Bill Clinton, as well as senior congressional leaders, before announcing bin Laden’s death to the nation.

Although Bush and former officials were quick to declare bin Laden’s killing a victory that transcended party lines, it represented the culmination of the former president’s promise, never fulfilled during his time in office, to capture the al-Qaeda leader “dead or alive.”

In a statement, Bush congratulated Obama and the military and intelligence personnel who “devoted their lives to this mission.”

“They have our everlasting gratitude,” Bush said. “This momentous achievement marks a victory for America, for people who seek peace around the world, and for all those who lost loved ones on September 11, 2001. The fight against terror goes on, but tonight America has sent an unmistakable message: No matter how long it takes, justice will be done.”

Obama announced bin Laden’s death eight years to the day after Bush declared the end of major combat operations in Iraq, a war spawned in large part by the Sept. 11 attacks, in front of a “Mission Accomplished” banner on the deck of an aircraft carrier.

Condoleezza Rice, Bush’s secretary of state, said in her own statement: “Nothing can bring back bin Laden’s innocent victims, but perhaps this can help salve the wounds of their loved ones.”

Victory for U.S.

Bin Laden, the son of a billionaire Saudi Arabian contractor, was wanted by the United States not only for the Sept. 11 hijackings but also for al-Qaeda’s bombings of U.S. embassies in Tanzania and Kenya in 1998, which killed 224 civilians and wounded more than 5,000 people. The U.S. government had offered a $25 million reward for information leading to his capture or death.

He was one of a handful of Islamist radicals who in 1988 founded al-Qaeda — which means “the base” in Arabic — to coordinate the efforts of various groups fighting the Soviet army in Afghanistan. After the Soviets withdrew from Afghanistan, al-Qaeda eventually shifted its effort to target another superpower: the United States.

A senior administration official said the loss of bin Laden puts al-Qaeda “on a path of decline that will be difficult to reverse.”

“As the only al-Qaeda leader whose authority was universally respected, he also maintained his cohesion, and his likely successor, Ayman al-Zawahiri, is far less charismatic and not as well respected within the organization, according to comments from several captured al-Qaeda leaders,” the official said. “He probably will have difficulty maintaining the loyalty of bin Laden’s largely Gulf Arab followers.”

That bin Laden was killed — rather than captured — was a victory itself for U.S. officials, who had dreaded the prospect of a long and complicated legal battle if he was taken into U.S. custody.

With the military brig at Guantanamo Bay no longer being used to house new detainees, and with the country paralyzed by the politics of where and how to try other alleged perpetrators of the Sept. 11 attacks, the logistics of trying bin Laden could have turned the capture into a spectacle. Now, although he might become a martyr to his supporters, it will be as an invisible hero.

“Every day he was alive was a symbolic victory,” said Dan Byman, director of research at the Saban Center for Middle East Policy at the Brookings Institution and professional staff member on the 9/11 Commission. “This is a man we have hunted with different degrees of intensity for more than 10 years. ... His successful defiance was damaging to the United States.”

Washington reacts

Obama’s announcement on Sunday seemed to electrify Washington and indeed the country. Hundreds of people streamed toward the White House with flags, some chanting “U.S.A.! U.S.A.!” In New York, many more were celebrating at Ground Zero and in Times Square.

Before Obama announced the killing, top administration officials divided up the most senior members of Congress and began making calls in the evening, according to congressional aides in both parties. Vice President Biden contacted Senate Minority Leader Mitch McConnell (R-Ky.); Defense Secretary Robert M. Gates called Sen. John McCain (Ariz.), the top Republican on the Senate Armed Services Committee; and Secretary of State Hillary Rodham Clinton called Sen. John F. Kerry (D-Mass.), chairman of the Senate Foreign Relations Committee.

Senior congressional leaders issued statements commending the military for the killing.

“Today, the American people have seen justice,” House Homeland Security Chairman Peter T. King (R-N.Y.), whose Long Island district lost many in the 2001 attacks, said in a statement. “In 2001, President Bush said, ‘We will not tire, we will not falter and we will not fail.’ President Bush deserves great credit for putting action behind those words. President Obama deserves equal credit for his resolve in this long war against al-Qaeda.”

Kerry urged vigilance, saying: “A single death does not end the threat from al-Qaeda and its affiliated groups.”

“The killing of Osama bin Laden closes an important chapter in our war against extremists who kill innocent people around the world,” Kerry added. “We are a nation of peace and laws, and people everywhere should understand that our 10-year manhunt was in search of justice not revenge.  Terrorists everywhere must never doubt that the United States will hunt them down no matter where they are, no matter how long it takes.”

Rep. Gary Ackerman (D-N.Y.) told CNN: “We’ve cut the head off of the worm, but they may grow another head.”

Minutes after the news broke on Sunday night, hundreds of people rushed to the White House to celebrate. Many were George Washington University students who were cramming for finals when someone alerted an entire dormitory building after seeing a bulletin on television.

“I feel like relief,” said freshman Molly Nostrand, 19, who was a fourth-grader in 2001. “After 10 years, it’s a sense of closure in a way.”

Those who arrived early to the impromptu street celebration sang “The Star-Spangled Banner” in roars and chanted “U.S.A.!” Many brought American flags and some put together signs.

“Ding, Dong, Bin Laden is Dead,” one read.

One group of waved a “Bush-Cheney 2000” election poster.

“I think it’s an accomplishment for the U S of A,” Richard Indoe, 73, a farmer from Ohio said, shortly after filming a few seconds of the revelry using a flip cellphone. “Too bad this didn’t happen during George W. Bush’s time.”

Staff writers Karen DeYoung, Ernesto Londoño, Glenn Kessler, Paul Kane, Felicia Sonmez and Amy Gardner contributed to this report.