THIS spooky video shows a flying saucer shaped cloud formation floating across the Moscow sky line.

The unusual weather phenomenon was filmed by an eyewitness with a smartphone who spotted it over the city's Adropov Avenue.

He is heard in the background of the video asking: "What is that? Aliens? Is it a UFO?"

The footage sparked a lively debate after it proved popular with viewers when it was posted on video-sharing platforms.

"Oh wow! I also spotted some weird-looking clouds in the city centre that day, but I thought I imagined it," said a man called Ilya.

"I wonder what will happen next?!"

Another viewer said: "I've been seeing things like that on the skyline for a while now, but previously they seemed a little less distinct.

"So does that actually mean that aliens do exist?"

Oksana Nikiforova said: "This looks just incredible!", while another person joked: "This is the end, isn’t it?!"

The UFO cloud is believed to have been an unusually-shaped cumulus – a fluffy low level cloud.

However, some observers speculated that it might have been a lenticular cloud.

They are often mistaken for UFOs because of their characteristic appearance and smooth saucer-like shape.