The mesmerising cloud looks similar to a hexagon and seems almost too perfect to be caused naturally, according to conspiracy theorists.
The incredible cloud formation was spotted on Wednesday morning over the Scandinavian country and quickly uploaded to social media by people who snapped it.
One person wrote on Twitter: “It is clearly a UFO”
Another added on Facebook: “For a certain cloud formation that’s not too common we sure are seeing them often. I’m finished accepting what ‘they’ want us to believe so from here on out we must question everything.”
While a third posted: “Cloaked UFO sitting at Cloud level. Just saying!”
However, the Finnish Meteorological Institute chipped in, stating the odd cloud was probably formed by ice crystals in the sky reacting with a ‘plate’ of droplets a bit lower down in the skies.
Paavo Korpela, a meteorologist with the Finnish Meteorological Institute, told Iltalehti: “That cloud layer, which is now there, is about six to seven miles (10-12km) high, and the temperature is over 20 degrees frost (12 Fahrenheit).
“One explanation could be that if ice crystals come from above cloud layers, it causes very rapid liquid water freezing in ice crystals, where clouds will rain down and evaporate at the same time.”
It is not the first time that civilians have been baffled by a cloud formation and cried alien.
Black rings have been spotted across the world, which some believe is a sign of alien activity.
In April, onlookers in the Russian city of Novosibirsk spotted tan odd black circular cloud, while in 2016, an almost identical one was spotted over Disneyland, California.
The numerous sightings have seen alien hunters clamouring to offer their opinions, with prominent UFO blogger Scott C Waring saying it is a type of extra-terrestrial space craft.
He wrote about the sighting over Disneyland: “Ring UFOs are super rare, but they have been seen.
“This UFO is over Disneyland and causes the family to worry about an alien invasion.”