Historians working in Germany and the US claim to have found a 60-year-old diagram showing a Nazi nuclear bomb.

It is the only known drawing of a "nuke" made by Nazi experts and appears in a report held by a private archive.

The researchers who brought it to light say the drawing is a rough schematic and does not imply the Nazis built, or were close to building, an atomic bomb.

But a detail in the report hints some Nazi scientists may have been closer to that goal than was previously believed.