The Nazi doctor named the "Angel of Death" for his experiments on Jewish prisoners was one of the shadowy figures behind the notorious Roswell incident, according to the author of a new book about alien invasions and cover-ups.

In her book Area 51: An Uncensored History of America's Top Secret Military Base, journalist Annie Jacobsen wrote that the "UFO" sighted in New Mexico in 1947 was actually the work of the Soviet authorities.

Ms Jacobsen claimed that before the Roswell crash, Soviet dictator Joseph Stalin recruited Nazi war criminal Josef Mengele to create "grotesque, child-size aviators" to pilot a plane.

She said Stalin's aim was to trigger widespread panic in America.

The author said she had consulted classified documents and interviewed former Area 51 workers for the book.

Her theory is the latest in a long list of conspiracies surrounding the Roswell crash.