The president of Pakistan has dismissed claims that his country harboured Osama bin Laden as "baseless speculation" as America said it was determined to find out how the figurehead remained undetected.
Asif Ali Zardari came out fighting after Pakistan was thrown into the spotlight when the al-Qa'ida leader was found living in an obviously unusual mansion near a military academy in the town of Abbottabad, 60 miles from the capital Islamabad.
Mr Zardari denied Pakistan "lacked vitality" in its fight against terrorism.
And he claimed his country was "perhaps the world's greatest victim of terrorism".
Writing in the Washington Post, he said: "Some in the US press have suggested that Pakistan lacked vitality in its pursuit of terrorism, or worse yet that we were disingenuous and actually protected the terrorists we claimed to be pursuing.
"Such baseless speculation may make exciting cable news, but it doesn't reflect fact.
"Pakistan had as much reason to despise al-Qa'ida as any nation.
"The war on terrorism is as much Pakistan's war as it is America's."
The leader acknowledged bin Laden's assassination was not a joint operation between his military and the Americans.
But he insisted a decade of co-operation and partnership between the countries led to his elimination "as a continuing threat to the civilised world".
The Americans had grave concerns about Pakistan intelligence leaking details of the assault and bin Laden being tipped off.
Therefore, they did not seek permission to stage the operation nor share its details.
The Pakistani authorities were only notified once the US Navy Seals had recovered the fundamentalist's body and left the country's airspace, White House counter-terrorism adviser John Brennan confirmed.
The tactic could have resulted in a clash if Pakistan's air force, which was scrambled, had arrived at the scene in time.
Though the US administration has stopped short of directly accusing Pakistan and its intelligence services of harbouring bin Laden, it said he clearly had a support network there.
"It is inconceivable that bin Laden did not have a support system in the country that allowed him to remain there for extended period of time," said Mr Brennan.
"We are going to pursue all leads to find out what kind of support system and benefactors that bin Laden might have had."
President Barack Obama - who personally authorised the mission to get bin Laden - watched the raid unfold in real-time with Secretary of State Hillary Clinton from the White House Situation Room.
As well as bin Laden, who was shot in the head, one of his adult sons, two suspected al Qaida couriers and a woman thought to be one of his wives died in the attack on the compound.
While a courier was painstakingly tracked to the premises, the Americans were unsure if bin Laden was present.
"It was probably one of the most anxiety-filled periods of time in the lives of the people assembled here," Mr Brennan said.
"The minutes passed like days."
Following the operation, bin Laden's identity was confirmed through DNA testing before being flown to an American warship in the Arabian Sea for burial at sea.
American officials were considering whether to release photographs of his body to counter suspicions in the Middle East that he was not really dead.
Many Western intelligence experts believe the world's most notorious terrorist may have received protection from elements within the ISI intelligence agency - some of whom are suspected of pro-al Qaida sympathies.
While it had long been thought that bin Laden was hiding in Pakistan, there was surprise that he was discovered in the northern town rather than the lawless tribal areas along the borders of Afghanistan.
The large, well-protected complex where he was living was said to be worth a million dollars but had no internet or telephone links which, analysts said, should have raised suspicions about who was there.
Prime Minister David Cameron last night spoke by telephone to Pakistani President Mr Zardari and Prime Minister Yusuf Raza Gilani in an attempt to soothe tensions.
Downing Street said Mr Cameron, who also spoke to Afghan President Hamid Karzai, said Britain was committed to working "extremely closely" with both countries to counter the terrorist threat from al Qaida and the Taliban.
Mr Cameron, who chaired a 45-minute meeting of the Government's Cobra emergencies committee, will update MPs on events in a Commons statement later today.
Meanwhile, Britain has followed the US in putting its embassies and military bases around the world on heightened alert amid fears of reprisals by al-Qa'ida and its affiliates.
Foreign Secretary William Hague said al-Qa'ida would want to show it was still "in business", while CIA director Leon Panetta said the terrorists would "almost certainly" try to avenge their leader.
Foreign Office Minister Alistair Burt was asked on BBC Breakfast if he agreed with suggestions from US officials that Pakistan must have known something about bin Laden's whereabouts.
"We do not know about that. What we do know is that Pakistan is a vital partner in counter-terrorism issues for the UK and for the rest of the world community," he said.
"They have lost a lot of their own security forces to terrorism, they are fighting it very hard in their own country, and of course they are playing a key role in Afghanistan.
"We don't know all the circumstances behind the location of bin Laden and the events yesterday but we do know that Pakistan will remain a very important security partner for us and for the international community."
Asked to comment on why he thought Pakistan was not informed about or involved in the raid, he said: "Again, that is an operational matter for the US.
"They had information which led them to believe that bin Laden was where he was and the US have made it clear in the past that if they had that information, they would feel able to act upon it.
"But that is a matter for them and their relationship with Pakistan and again I do not think we have the operational details fully and we don't have the intelligence information in terms of the lead-up to that."
Asked to comment on the threat to the UK, he said: "We have not needed to change the general threat level to UK citizens, but it is just a matter of common sense at the moment.
"There might be places that they would avoid in terms of large crowds, potential demonstrations and things like that.
"We are just warning UK citizens first of all to look at the Foreign Office website and the travel advice and just be extra careful."
He added: "We are trying to be sensible and cautious in the light of events yesterday.
"There is a concern that there might be some form of reprisal so we have heightened the security around all our embassies and consulates around the world, particularly Afghanistan and Pakistan, but we have nothing to indicate a specific threat."
Cricketer-turned-opposition politician Imran Khan said: "Never have I seen such embarrassment in Pakistan amongst the people and also fear - fear that we are now in a nutcracker situation."
On one hand it appeared the Pakistan intelligence agency "was actually protecting Osama bin Laden" but on the other the leadership said it had provided intelligence for the mission.
That would result in pressure for a renewed military crackdown on extremists, further fuelling the possibility of revenge attacks in Pakistan's towns and cities, he suggested.
"For Pakistanis this has been a total disaster. There is a lot of fear. Everywhere I go people are worried about the fall-out," he told Today.
Labour leader Ed Miliband said the US actions had been right and praised the "professionalism" of the operation.
Asked if he would rather have seen the al Qaida chief taken alive and put on trial, he said: "I do not think it's right to second guess this operation. This was a very, very complex operation conducted in great secrecy.
"The opportunity was offered, as I understand it, for Osama bin Laden to surrender. He did not.
"We should all look forward. The world is now a safer place ... a good thing for the world, for people of all faiths and all civilisations.
"It was right what the United States did and actually I pay tribute to the professionalism and the skill of the operation."
He said his opposition to Guantanamo remained unchanged and that the use of torture was never justified.
"I am not saying that has anything to do with this case but I think you should always make sure there is proper decency in relation to prisoners."Reuse content