A UFO researcher has released images of an alien which he claims he obtained from a US intelligence agent after an autopsy was performed in the top-secret Area 51.

Tom Carey said the footage (not pictured) was captured on film and has been verified by Kodak to date back to 1947 – the same year of the infamous Roswell incident in New Mexico, the Mirror reports.

"What's interesting is, the film is dated 1947," Carey said. "We took it to the official historian of Kodak up in Rochester, New York, and he did his due diligence on it, and he said yes, this filmstrip, the slides are from 1947. It's 1947 stock."

"And from the emulsions on the image, it's not something that's been Photoshopped like today," Carey added.

"It's original 1947 images, and it shows an alien who's been partially dissected lying in a case."

Carey described the alien as being four feet tall with an insect-like head.

"The head has been severed, and there's been a partial autopsy," he said. "The innards have been removed, and we believe the cadaver has been embalmed, at least at the time this picture was taken."

Nigel Watson, author of the Haynes UFO Investigations Manual, said: "Usually when people make promises that they have the smoking gun of ufology – positive evidence of their existence – they come to nothing or they produce rather underwhelming evidence.

"However, if aliens were retrieved it would be a world-changing event and I can't imagine they could keep the lid on such an event throughout the 1950s and 1960s."

Earlier this year, a Pennsylvania woman claimed to have recorded video footage of UFOs flying over her house.

Stephanie Wilkerson said she was on the porch of her home in Lower Paxton Township when she noticed the objects flying overhead.

"I thought it was a plane until I realised it wasn't moving," Wilkerson told ABC. "I watched it for about 20 minutes and I started noticing it changing colours."