A flying saucer-shaped cloud has been spotted in the skies above Romania – just weeks after a similarly striking formation appeared over Moscow.
If viewed from a distance the disc cloud, which is outlined by a ring of sunlight, appears to resemble an alien craft.
Meteorologists explained that the phenomenon witnessed in Moscow was just an optical effect produced by rare weather conditions, but the latest clip – apparently filmed at the end of last week – has again set tongues wagging.
"How come I have never seen clouds that look like that. Now we get two in a matter of weeks in different places," wrote one user of the video-sharing website Live Leak where the clip was first posted.
Others speculated – with tongues firmly in cheeks – that the twin formations could herald an alien invasion.
"Run the two videos and put them beside each other... It's very strange... are they here?" commented a user named Raginswirler.
The two clips appear to show a formation known as a "fallstreak hole", which occurs when moisture in the air cools below 0C but is unable to turn into ice.
While most of the "supercooled" water remains suspended in the sky, rings of ice do form and plunge to earth, leaving doughnut-shaped holes in the cloud layer.
The luminous effect visible in the Russian and Romanian videos is due to the the sun being low in the sky.
- Daily Telegraph