NATO officials are worried that their organization may be investigated by the International Criminal Court after its prosecutor said allegations of crimes committed by NATO in Libya would be examined "impartially and independently," according to diplomats accredited to NATO headquarters.

The diplomats said action to pre-empt a war crimes investigation would likely include an immediate internal legal review of all incidents in which NATO bombing or other actions caused civilian casualties.

They spoke on condition of anonymity because of the sensitivity of the issue.

The alliance has always maintained that its operations in Libya were carried out strictly in keeping with a U.N. Security Council resolution that authorized member states "to take all necessary measures to protect civilians and civilian populated areas under threat of attack" in the North African country.

NATO leaders have repeatedly hailed the precision with which the mission was carried out, citing the small number of civilian deaths caused by the bombing as evidence of its success.

Still, in a briefing to the Security Council on Nov. 2, International Criminal Court prosecutor Luis Moreno-Ocampo said "there are allegations of crimes committed by NATO forces (and) these allegations will be examined impartially and independently."

Moreno-Ocampo did not elaborate further on the accusations against NATO forces, or who was making them. His office is currently focusing on crimes committed by members of the ousted Gadhafi regime and is waiting for a report by a U.N. Commission of Inquiry in Libya, due in March, before deciding whether to proceed with a formal investigation into alleged crimes by NATO.

NATO has said it was confident its actions were in compliance with international law. "In the event we receive a request for information, NATO is prepared to assist in any way it can," said an official who could not be identified under standing rules.

Officials from the alliance say that between March and October NATO warplanes flew 26,000 sorties, including more than 9,600 strike missions, destroying more than 1,000 tanks, vehicles, and guns, as well as buildings claimed to have housed "command and control" centers. These included facilities such as Moammar Gadhafi's heavily fortified compound in Tripoli, but also residential homes of his supporters -- targets which could be considered outside the UN mandate.

NATO is already involved in a civil suit in Belgium that accuses the alliance of killing 13 civilians in the bombing of a residential compound near Libya's capital, Tripoli. Attorneys for the plaintiffs say that, although NATO and other international organizations enjoy diplomatic immunity in criminal cases, they fall under Belgian jurisdiction in civil suits.

The immunity applies only to those holding diplomatic status.

The definition of war crimes, as described by international conventions on the laws of war, includes any destruction of civilian targets not justified by military necessity. It has been invoked in a number of trials dealing with a number of conflicts, including those in Bosnia, Croatia and Kosovo.

The possibility of an ICC probe is already causing friction within the alliance, officials said. At a meeting last week of NATO ambassadors and their counterparts from partner countries, the Russian ambassador, Dmitry Rogozin, noted a number of airstrikes could be considered potential war crimes. But envoys from some nations that participated in the bombing reacted angrily, describing the comment as "libel."

A French Rafale fighter-bomber is said to have bombed a convoy of vehicles fleeing Gadhafi's besieged hometown of Sirte last month, resulting in the capture and subsequent killing of the dictator by opposition forces.

The incident is particularly controversial because during the siege -- characterized by massive shelling of Sirte's downtown area by the former rebels -- NATO warplanes never struck the attackers. Instead, they attacked a fleeing convoy of civilian vehicles.

Lt. Gen. Charles Bouchard, the Canadian who commanded the NATO operation, explained that commanders ordered the strikes because they believed the convoy would try to link up with other pockets of pro-Gadhafi resistance in the west.

While Moreno-Ocampo has said allegations of NATO crimes would be examined, that does not necessarily mean he will open a formal investigation. Depending on the U.N. commission's findings, he could decide there is no need for further investigations or ask judges for authorization to open a formal probe. He could also determine that there are proceedings at the national level that would negate the need for a case to be brought before the ICC, a court of last resort.

"We are not talking about any specific incident. We are saying, 'Yes, if there are allegations of crimes we will review that,"' Moreno-Ocampo told The Associated Press.

Currently, nearly 120 states are parties to the ICC. All European NATO members and Canada have accepted its jurisdiction.

Since NATO is not a signatory to the ICC treaty, it would appear likely that any violations of the conventions on the laws of war would require direct dealings between the court and its member states, and not with NATO as an institution.

The operation's critics -- including Russia, China and the African Union -- have argued that NATO misused the limited U.N. resolution as a pretext to promote regime change in Libya. Its daily air raids were instrumental in enabling the ragtag rebel forces to advance on Tripoli and later capture the rest of the country.

The issue threatens to have far-reaching consequences for future U.N. interventions.

Russia and China have already vetoed a Security Council resolution that would have imposed sanctions on Syria for its violent crackdown on opposition demonstrators, arguing that NATO could again misuse a U.N. measure to justify months of air strikes.

"If there were to be evidence that NATO is also involved in activities illegal under international law, something should be done about that," said Nicolas Beger, director of the Amnesty International European Institutions office. "Nobody should be allowed to commit war crimes, and nobody should be able to get away with it."

He also said there needed to be an impartial probe into Gadhafi's death.

"If he was captured alive and then killed, that's a war crime. That's clear."