The video released on YouTube shows what looks like a flat disk-shaped cloud floating through the sky in Arizona.

Anthony Sakowski, who captured the footage, said he thought the cloud could be hiding something more sinister.

He wrote: “Strange cloud hiding UFO. Reflected above.”

The lighter parts are the thin cloud as the sun shines through it. Even cloaked in a cloud, this is clearly a UFO.

“It’s metallic surface is a different surface than anything in the sky or the ground.”

But others weren’t so sure, saying the footage could be explained more simply by a rare weather phenomenon called a lenticular cloud.

The rare stationary and oval-shaped clouds are often mistaken for UFOs.

The latest reported sighting comes after a bizarre UFO rock baffled experts and sparked fears of an ancient alien civilisation.

Just last week Chilean officials released top secret video footage of a UFO “leaking gas” which they were unable to explain.