THE world is today on red alert after terrorist leader Osama bin Laden was killed in a daring raid by US special forces.

The world’s most wanted man, who inspired numerous atrocities, from the 9/11 attacks in the US to the July 7 London bombings, was shot dead in a town 35 miles from the Pakistani capital Islamabad, raising global concerns of revenge attacks.

While US President Barack Obama has hailed the death of the 54-year-old al Qaeda leader as a “good day for America,” saying “the world is a safer and a better place”, members of militant Islamist forums were already vowing to avenge the killing.

The American intelligence agency, the CIA, warned retaliation was almost certain. “Although bin Laden is dead, al Qaeda is not,” said CIA director Leon Panetta. “The terrorists almost certainly will attempt to avenge him, and we must remain vigilant.”

US officials said that, as well as bin Laden, three other men and a woman, believed to be his wife, died in the raid. The woman was said to have been used as a human shield, although it is not known whether she placed herself in the line of fire or was put there.

Bin Laden’s body was swiftly buried at sea, with US officials saying it would have been difficult to find a country prepared to accept the remains of such an infamous figure.

Officials said his identity was confirmed with “99.9% confidence” by DNA testing after he was killed by a precise “double tap” shooting to the head.

Bin Laden’s death marked the end of an international manhunt lasting more than a decade for the figurehead behind a campaign of Islamist violence that has sparked wars in Afghanistan and Iraq and claimed thousands of lives around the world. While it had long been suspected he had been hiding in Pakistan, there was surprise when he was finally tracked down to a plush mansion complex close to a leading military academy.

The discovery he had been living in the garrison town of Abbottabad, rather than the lawless tribal areas of the north-west frontier, prompted fresh suspicions that he was being protected by Pakistan’s intelligence services.

While US intelligence officials said Pakistani authorities did not know bin Laden was sheltering there, John Brennan, Mr Obama’s top counter-terrorism adviser, said it was inconceivable that bin Laden did not have some support in Pakistan.

Mr Brennan said the White House was talking to the Pakistani government and pledged to pursue all leads to find out what type of support system or benefactors bin Laden might have had.

The announcement of bin Laden’s death sparked jubilant celebrations in America, with crowds gathering outside the White House and at Ground Zero where the Twin Towers had stood in New York.

In a statement broadcast from the White House, Mr Obama said the operation had been carried out by a “small team of Americans acting with extraordinary courage and capability”.

He added: “On nights like this one, we can say to those families who have lost loved ones to al Qaeda’s terror: justice has been done. The cause of securing our country is not complete. But tonight, we are once again reminded that America can do whatever we set our mind to.”

David Cameron, who last night chaired a meeting of the Government’s Cobra emergencies committee, said bin Laden’s death was “a massive step forward”.

“Of course, nothing will bring back those loved ones that families have lost to terror. But at least they know the man who was responsible for these appalling acts is no more,” he said.

However, there were sinister warnings emerging from Jihadist forums.

Asad al-Jihad 2, labelled a “prominent member of the jihadist internet community” by the monitoring group SITE, said: “We will take our revenge on behalf of the Islamic Ummah for the death of the Sheikh of Islam ... Whoever wishes this to be the end of jihad or a means to weaken the organisation, I say to him: Wait a little.”

Another poster said: “Oh God, please make this news not true ... God curse you Obama, Oh Americans ... it is still legal for us to cut your necks.”

In Afghanistan, President Hamid Karzai urged the Taliban not to seek retaliation and the leader of the Palestinian terror group Hamas condemned bin Laden’s killing as the assassination of “a Muslim and Arabic warrior” and said it marked “the continuation of the American oppression and shedding of blood of Muslims and Arabs”.

Britain followed the US in placing its embassies, diplomatic missions and military bases around the world on a heightened state of alert.

Foreign Secretary William Hague said elements within al Qaeda and its affiliates would want to show they were still “in business”.

Irene Sword, the mother of 29-year-old Derek Sword, a young banker from Dundee who died in the 9/11 attacks on the World Trade Centre, said she hoped the killing did not encourage his “supporters around the world to take up his mantle”.

Pakistan’s former president, Pervez Musharraf, said the US raid to kill bin Laden was a “violation of our sovereignty” while Pakistan’s Foreign Office termed it “a major setback to terrorist organisations around the world”.

Troops from the US Navy’s Seal Team Six counter-terrorism unit, were flown by MH-60 Blackhawk helicopters into the compound in an operation lasting less than 40 minutes.