UK vigilance urged after Osama Bin Laden death
Britons have been urged to be vigilant in the wake of the death of al-Qaeda leader Osama Bin Laden, with embassies worldwide ordered to review security.
Bin Laden, believed to be behind the 9/11 attacks, was killed by US forces about 62 miles from Pakistan's capital.
Prime Minister David Cameron hailed the death as "a great success" but said it was not the end of terror threats.
He chaired a 45-minute meeting of the UK's emergency response committee, Cobra in the evening.
A Downing Street spokesperson said: "The group welcomed the president's announcement and agreed it was an important step forward in the fight against terror.
"The group also discussed the potential impacts of the incident. They agreed to continue to make every effort to counter terrorism and extremism."
The meeting of the committee came after Mr Cameron spoke with President Hamid Karzai of Afghanistan, and President Asif Ali Zardari and Prime Minister Yusuf Raza Gilani of Pakistan on Monday.
Downing Street said: "The prime minister made clear in the conversations that Britain would continue to work extremely closely with both Afghanistan and Pakistan to tackle the terrorist threat from al-Qaeda and from the Taliban."
The Foreign Office has urged Britons overseas to "exercise caution in all public places and avoid demonstrations, large crowds of people and public events".
Defence Secretary Liam Fox has also ordered British military bases - both in the UK and abroad - to maintain a "high level of vigilance".
Mr Cameron was phoned by US President Barack Obama before dawn on Monday UK time, a couple of hours before the president announced the news in a televised address.
Speaking later from the prime minister's country residence, Chequers, he said: "This news will be welcomed right across our country.
"Of course, it does not mark the end of the threat we face from extremist terror - indeed we will have to be particularly vigilant in the weeks ahead. But it is, I believe, a massive step forward."
The PM plans to make a statement to the House of Commons on Tuesday afternoon.
Following Bin Laden's death, the US put its embassies around the world on alert, warning Americans of the possibility of al-Qaeda reprisal attacks for Bin Laden's killing.
Foreign Secretary William Hague said the network may try to reassert itself and stressed the likelihood of reprisals against UK targets.
"We must remember that this is not the end of being vigilant against al-Qaeda and associated groups, and, in fact, there may be parts of al-Qaeda that will try to show that they are still in business in the coming weeks, as indeed some of them are.
"So I have already this morning asked our embassies to review their security, to make sure that vigilance is heightened - and I think that will have to be our posture for some time to come.
"This is a very serious blow to al-Qaeda, but like any organisation that has suffered a serious blow, they will want to show in some way that they are still able to operate."
End Quote Nick Robinson BBC News political editor
Today's news of the death of Osama Bin Laden could have a profound effect on the decisions taken about the future.”
Home Secretary Theresa May said Bin Laden's death was "an important and significant development in the struggle against global terrorism" but there was still a "real and serious threat".
"There is a continuing need for everyone to remain vigilant and to report any suspicious activity to the police," she said.
The threat level to the UK from international terrorism has remained at severe since January 2010, indicating a terrorist attack is highly likely.
The Joint Terrorism Analysis Centre, which includes representatives from 16 government departments and agencies, sets the threat level.
Bin Laden was top of the US "most wanted" list, and President Obama said his death was "the most significant achievement to date in our nation's effort to defeat al-Qaeda".
In the attacks in New York and Washington on 11 September, 2001, 67 Britons were among the 3,000 people killed when four planes were hijacked and flown into New York's World Trade Center, the Pentagon and a field in Pennsylvania.
Tony Blair, UK prime minister at the time of the attacks, expressed his "heartfelt gratitude to President Obama and to all of those who so brilliantly undertook and executed this operation".
"We should never forget 9/11 was also the worst ever terrorist attack against UK civilians, and our thoughts are with all those - American, British and from nations across the world - who lost their lives and with their loved ones who remain and who live with their loss.
"The operation shows those who commit acts of terror against the innocent will be brought to justice, however long it takes."
Labour leader Ed Miliband, while reiterating the call for vigilance, said: "The world is a safer place as a result of the death of Osama Bin Laden because he is no longer there to command or encourage terrorism."
Farooq Murad, the secretary general of the Muslim Council of Britain, said few would mourn the death of Bin Laden, "least of all Muslims".
"Many Muslims will reflect on the 10 years that have passed in which our faith and our community have been seen through the prism of terrorism and security.
"His extremism has been responsible for the deaths of many people, including many Muslims around the world."
Those who follow Bin Laden may now wish to show that the death of their leader has not affected their ability to pursue his agenda of violence.
Pakistan's main Taliban faction has already threatened to attack the country's rulers and the US and the Foreign Office has urged Britons overseas to "exercise caution". The prime minister also made clear there is a need for particular vigilance in the weeks ahead.
Many groups affiliated to al-Qaeda - like the offshoot in Yemen which has been most active in recent months - will be barely affected by Bin Laden's death operationally.
The Home Office in London is making clear the threat level will remain where it is - at the second highest level, meaning an attack is highly likely.
However, al-Qaeda supporters have been trying to carry out a successful, major attack for many years and even if their desire may be increased by Bin Laden's death, their ability to actually do so will not have changed. Any violence is therefore more likely to be low-level.
But while the fear is of reprisals in the short term, the hope will be that the death will - in the longer term - help erode the appeal of al-Qaeda's ideology.
Bin Laden evaded the forces of the US and its allies for almost a decade, despite a $25m (£15m) bounty on his head.
He was killed in a firefight in a fortified residence in Abbottabad, 100km (62 miles) north-east of Islamabad.
Mr Hague acknowledged that there had been a "general assumption" that Bin Laden was hiding in the mountainous, tribal regions of Pakistan rather than the area around the capital, Islamabad.
But he added: "I don't think we're surprised by anything any more."
Deputy Prime Minister Nick Clegg added his praise - and caution - about the operation: "This successful US operation is a major step forward and a serious blow to al-Qaeda but it does not mean that the struggle against terrorism is over."
Shadow foreign secretary Douglas Alexander said that since 9/11, there had been a continued international focus to bring Bin Laden to justice, "but frankly there were periods during those 10 years when it was far from certain where Bin Laden was or even that the trail had not gone cold".
"There will be plenty of time for questions to be asked and answers offered," he said, adding that immediate steps needed to be taken to keep everybody safe.