The Archbishop of Canterbury has said that the killing of an unarmed Osama bin Laden by US special forces left him with a "very uncomfortable feeling".
Rowan Williams also criticised the way in which the Obama administration has appeared to change its account of the raid. Asked about any moral justification for the al-Qaida leader's death in Pakistan, he 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.
"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."
Williams is the latest religious leader to comment on the ethics of the killing of Bin Laden. On Monday a Vatican spokesman, Father Federico Lombardi, said that while Christians "do not rejoice" over a death, it serves to remind them of "each person's responsibility before God and men".
"Osama bin Laden, as everyone knows, had the grave responsibility of having spread division and hate among people, causing the deaths of an innumerable number of people and exploiting religion for these purposes," he said.
Pakistan's foreign secretary also raised fresh doubts about the legality of killing Bin Laden. Clutching UN security council documents, Salman Bashir said: "There are legal questions that arise in terms of the UN charter. Everyone ought to be mindful of their international obligations."
His comments, at a press conference in Islamabad, may have been aimed as much at preventing India from launching a unilateral raid on Pakistani territory in revenge for the 2008 Mumbai massacres as reproaching Washington.
Bashir added that this "violation of sovereignty, and the modalities for combating terrorism, raises certain legal and moral issues which fall ... in the domain of the international community".
As more detailed accounts of the assault on Bin Laden's compound by US special forces emerged, international lawyers and human rights groups also called for justification of the raid's legitimacy.
The International Committee of the Red Cross discussed the case in Geneva. "The ICRC do not ... have enough facts to assess the legal and humanitarian implications," a spokesman said. "Should we have any issues we will refer them [to Washington] confidentially".
Earlier this week, the UN's independent investigator on extrajudicial killings, Christof Heyns, said there was "considerable dispute in legal circles as to whether we are dealing with an armed conflict in respect of al-Qaida in Pakistan".
Nick Grief, an international lawyer at Kent University, said that the attack had the appearance of an "extrajudicial killing without due process of the law". He added: "It may not have been possible to take him alive ... but no one should be outside the protection of the law." Even after the end of the second world war, Nazis had been given a fair trial before being punished as war criminals, Grief added.
In Cuba, Fidel Castro, was unequivocal. The US president, he wrote, "has no way to hide that Osama was executed in the presence of his children and wives".
Following years of targeted killings by US drones along the Afghan/Pakistan border and in Yemen, the death of Bin Laden plays into a climate of legal and political suspicion about the lawfulness of American overseas strikes.
The UN's high commissioner for human rights, Navi Pillay, appealed for "full disclosure of the accurate facts" to determine the legality of the killing.
Comparisons between Bin Laden and Nazi war criminals have set the context for debates over whether greater effort should have been made to capture the founder of al-Qaida alive and bring him to justice in an international court.
The writer Toby Young said that a different second world war analogy applied, since al-Qaida had not surrendered, unlike the Nazis in 1945. Comparisons should not be with Nazi war trials, he wrote, "but with the plot to assassinate Hitler ... Had the allies succeeded in assassinating any of the Nazi leaders during the second world war, we would have applauded those responsible."
Most legal opinion in the United States has accepted the White House's rationale that the US is at war with al-Qaida. Steven Ratner, a professor at the University of Michigan law school, said: "A lot of it depends on whether you believe Osama bin Laden is a combatant in a war, or a suspect in a mass murder."
If Bin Laden was a combatant, then "whether he has a gun or not really doesn't matter", since it was lawful to kill combatants. The US administration has asserted that Bin Laden had two weapons within reach when shot.
David Scheffer, of Northwestern University school of law, pointed out that Bin Laden was indicted in a Manhattan court in 1998 for conspiracy to attack US defence installations. "Normally when an individual is under indictment, the purpose is to capture that person to bring him to court to try him. The object is not to summarily execute him if he's under indictment."
Such questions may only be resolved if the instructions given to the US Navy Seals are published and clarification given about what efforts were made to force Bin Laden to surrender.