The Archbishop of Canterbury says the killing of Osama bin Laden while he was not armed has left him with "a very uncomfortable feeling".

Bin Laden was shot dead in his compound in Abbottabad, Pakistan, and it later emerged he was unarmed when U.S. commandos fired at him.

Dr Rowan Williams said: "I think the killing of an unarmed man is always going to leave a very uncomfortable feeling because it doesn't look as if justice is seen to be done.

"In those circumstances I think it's also true that the different versions of events that have emerged in recent days have not done a great deal to help.

"I don't know the full details any more than anyone else does. But I do believe that in such circumstances when we are faced with someone who was manifestly a war criminal in terms of the atrocities inflicted it is important that justice is seen to be served."

The former head of the British Army, General Lord Dannatt, who is a practising Anglican, defended the action of the U.S. special forces.

He said that while in "ideal circumstances" they would have arrested bin Laden, in the event his killing had been "unfortunate but necessary".

"The special forces troops going in had been briefed, perfectly reasonably, that if bin Laden was anything other than naked, he could be assumed to be wearing a suicide vest," he told BBC Radio 4's PM programme.

Sir Paul Stephenson, Britain's most senior police officer, said terrorist action in the UK is now highly likely and could occur without warning at any time.

"Osama bin Laden led an organisation which is responsible for the injury and death of thousands of people worldwide in the name of an extreme and perverted ideology, committed to the use of terror and murder to achieve their aims," he said.

"However, one man's death does not mark the end of an ideology and we must remain alert to the continuing threat from al-Qaida, its affiliates and those acting alone."