WASHINGTON/ABBOTTABAD, Pakistan - World leaders warned of revenge attacks after Osama bin Laden was killed in a US assault in Pakistan on Monday that brought to a dramatic end the long manhunt for the al Qaeda leader who had become the most powerful symbol of Islamist militancy.

President Barack Obama declared the world was a safer and "better place" with bin Laden dead. But the euphoria that drew flag-waving crowds to "Ground Zero" of the September 11, 2001, attack in New York was tempered by calls for vigilance against retaliation by his followers.

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The revelation that bin Laden had been holed up in a compound near Islamabad threatened to exacerbate US tensions with nuclear-armed Pakistan, which had not been told of the raid in advance.

The White House acknowledged there was good reason for US lawmakers, already doubtful of Pakistan's cooperation against al Qaeda, to demand to know whether bin Laden had been "hiding in plain sight" and to raise questions about continued US aid to Islamabad.

Bin Laden was given a sea burial after Muslim funeral rites on a US aircraft carrier. His shrouded body was placed in a weighted bag and eased into north Arabian Sea.

The death of bin Laden, who achieved near-mythic status for his ability to elude capture for more than a decade, closes a bitter chapter in the global fight against al Qaeda, but it does not eliminate the threat of further strikes.

Under bin Laden's leadership, al Qaeda militants struck targets from Indonesia to the European capitals of Madrid and London.

But it was the September 11, 2001, attacks, in which al Qaeda militants used hijacked planes to strike at economic and military symbols of American might and killed nearly 3,000 people, that helped bin Laden achieve global infamy.

Those attacks spawned two wars, in Afghanistan and Iraq, inflicted damage on US ties with the Muslim world that have yet to be repaired, and redefined security for air travelers.

"Even as we mark this milestone, we should not forget that the battle to stop al Qaeda and its syndicate of terror will not end with the death of bin Laden," US Secretary of State Hillary Clinton said just hours after bin Laden was killed.

NIGHT RAID NEAR ISLAMABAD

A small US strike team, dropped by helicopter to bin Laden's hideout near the Pakistani capital Islamabad under the cover of night, shot dead the al Qaeda leader with a bullet to the head.

One of bin Laden's wives was thought to have been used to shield him at first, White House counterterrorism chief John Brennan told reporters. She was killed, along with one of bin Laden's sons, in the 40-minutes of fighting.

Television pictures from inside the house showed bloodstains smeared across a floor next to a large bed.

Obama and his staff followed the raid minute by minute via live video feed in the White House situation room, and there was relief when the commandos, including members of the Navy's elite Seals unit, stormed the compound.

"We got him," the president said, according to Brennan, after the mission was accomplished.

"Yesterday is a defining moment in the war against al Qaeda, the war on terrorism, by decapitating the head of the snake known as al Qaeda," Brennan said.

Mindful of possible suspicion in the Muslim world, a US official said DNA testing showed a "virtually 100 percent" match with the al Qaeda leader.

The discovery that bin Laden was living in a three-story residence in the military garrison town of Abbottabad, and not as many had speculated, in the country's lawless western border regions, is a huge embarrassment to Pakistan, whose relations with Washington have frayed under the Obama administration.

While some intelligence officials said there was no indication Pakistani authorities knew bin Laden was sheltering 35 miles (60 km) north of Islamabad, US lawmakers insisted Pakistan give an explanation.

Reflecting a lack of trust between the two countries, Washington did not tell Pakistan about the raid in advance.

"A number of people have questions about whether or not there was some type of support (for bin Laden) that was provided by the Pakistani government," Brennan said. "People are raising these questions, and now we're going to have to deal with them."

Obama, whose popularity has suffered from continuing US economic woes, will likely see a short-term bounce in his approval ratings. At the same time, he is likely to face mounting pressure from Americans to speed up the planned withdrawal this July of US forces from Afghanistan.

However, bin Laden's death is unlikely to have any impact on the nearly decade-long war in Afghanistan, where US forces are facing record violence by a resurgent Taliban.

Many analysts see bin Laden's death as largely symbolic since he was no longer believed to have been issuing operational orders to the many autonomous al Qaeda affiliates.

"There are a lot of al Qaeda look-alike cells," said Steve Clemons, a Middle East analyst at the New America Foundation. "Bin Laden was an animating force but there are other ways these groups get oxygen and can remain a threat."

Financial markets were more optimistic. The dollar and stocks rose, while oil and gold fell, on the view bin Laden's death reduced global security risks.

BURIED AT SEA, WARNINGS OF REVENGE

Analysts warned that objections from some Muslim clerics to the sea burial could stoke anti-American sentiment. The clerics questioned whether the United States followed proper Islamic tradition, saying Muslims should not be buried at sea unless they died during a voyage.

The United States issued security warnings to Americans worldwide. CIA Director Leon Panetta said al Qaeda would "almost certainly" try to avenge bin Laden's death.

France's President Nicolas Sarkozy hailed the killing as a coup in the fight against terrorism, but he, too, warned it did not spell al Qaeda's demise. British Prime Minister David Cameron said the West should be "particularly vigilant."

Vows to avenge bin Laden's death appeared quickly in Islamist militant forums, a key means by which al Qaeda leaders have passed on information. "God's revenge on you, you Roman dog, God's revenge on you crusaders," one forum member wrote.

A US national security official said there was no fresh intelligence suggesting new plots against US or other Western interests since bin Laden's death.

It was the biggest national security victory for the president since he took office in early 2009 and will make it difficult for Republicans to portray Democrats as weak on security as he seeks re-election in 2012.

In Saudi Arabia, bin Laden's native land, there was a mood of disbelief and sorrow among many. The Palestinian Islamist group Hamas mourned bin Laden as an "Arab holy warrior."

But many in the Arab world felt his death was long overdue. For many Arabs, inspired by the popular upheavals in Egypt, Libya and elsewhere over the past few months, the news of bin Laden's death had less significance than it once might have.