Secret budget documents show that a US military laboratory in Afghanistan analysed DNA from Osama bin Laden's corpse and confirmed his identify shortly after he was killed by a Navy commando team.

The Pentagon denied more than a year ago it had any records of these tests in a response to a freedom of information request filed by the Associated Press a day after President Barack Obama announced bin Laden's death.

The Washington Post reported on Thursday that classified intelligence budget files provided by National Security Agency whistleblower Edward Snowden stated that a forensic intelligence laboratory run by the Defense Intelligence Agency performed the DNA testing. The Post reported that the tests "provided a conclusive match".

The AP's request for records submitted on 2 May 2011 included DNA and facial recognition tests performed to ensure the body was bin Laden's, all videos and photographs taken during the raid on bin Laden's compound in Abbottabad, Pakistan, the death certificate and other records related to the mission.

Responding in March 2012, the defence department said it could not locate any of the files.

The AP reported in July that the nation's top special operations commander, Admiral William McRaven, had ordered military files about the raid purged from defence department computers and sent to the CIA, where they could more easily be shielded from being made public.

The secret move appeared to have sidestepped federal rules and perhaps the Freedom of Information Act. The CIA has special authority to prevent the release of "operational files" in ways that cannot effectively be challenged in federal court.

Spokesmen for the Pentagon and CIA denied the move was intended to avoid the legal requirements of the information act. The bin Laden mission was overseen by the CIA, they said, which meant the records about the raid should be housed with the spy agency.

The CIA has not responded to a separate request for many of the same records about the bin Laden mission the Pentagon said it could not find.