First thousands reportedly saw a ghostly alien city floating over Foshan in the Guangdong province of China.
A few days later people in the province of Jiangxi, China, also reported seeing a similar cloud city.
Thousands of people were said to be stunned by the apparition
Fata Morgana can be seen on land or sea and involves the optical distortion and inversion of distant objects such as boats, which can appears as skyscrapers because the images become stacked, when rays of light bend as they pass through air of different temperatures such as in a heat haze.
But the mystery has sent conspiracy theorists into over drive.
YouTube channel Paranormal Crucible said in a video report: “The footage captured by a local resident appears to show a huge city floating in the clouds.
“The apparition, which was witnessed by hundreds of shocked residents, only lasted a few minutes before completely disappearing.”
The channel speculated it could be “the result of a project blue beam test.”
Project Blue Beam is a prolific conspiracy theory which believes NASA will one day
simulate an alien invasion of Earth or second coming of Christ through holograms.
The story was so strange in made Chinese TV news channels
One online poster noted: “Notice the group of buildings is repeated three times? If it isn’t someone making it on their computer, it seriously could be project blue beam.”
The Paranormal Crucible video added: “But added: “Or a temporal vortex, a possible parallel universe material briefly into our own reality.”
“It is also possible, considering China’s technological achievements that a top secret holographic technology was tested over a heavily populated area in an effort to gauge the public reaction.”