Australia's military has lost its "X-Files", detailing sightings of unidentified flying objects (UFOs) across the country, a newspaper report said on Tuesday.

After a two-month search in response to a newspaper Freedom of Information (FOI) request, which forces government officials to release documents of public interest, Australia's Department of Defense had been unable to locate the files, the Sydney Morning Herald said.

"The files could not be located and Headquarters Air Command formally advised that this file is deemed lost," the department's FOI assistant director, Natalie Carpenter, told the paper. Defense officials could not be contacted.

The only file the defense department had been able to locate was a folder called "Report on UFOs/Strange Occurrences and Phenomena in Woomera", a military weapons testing range in the center of Australia's vast outback, Carpenter said.

All other files had been lost or destroyed, which the Herald said could fuel conspiracy theories about their disappearance.

The single remaining file detailed a sketchy series of sightings from around the country and overseas, including people living in towns near Woomera, in South Australia state.

X-Files, named after a popular US television science fiction program, refer to supposed government records detailing paranormal mysteries, usually involving fictitious alien species.

Australia's military had decided to stop taking UFO sighting reports in late 2000, the Herald said, asking members of the public to report incidents to police instead.