The picture was taken by a fisherman on board a Finnish trawler in international waters southwest of the capital Helsinki. The fisherman, who asked not to be named, said the sub was 800 meters away and heading east.
“Submarines use certain types of signals when they are surfaced and, moving closer, we could clearly see its silhouette,” he added.
Meanwhile, Finnish Coast Guard officials said the snapshot gave no reason for worry.
“Submarines are built at St. Petersburg shipyards and are often tested off Gotland Island in the Baltic, Finnish Coast Guard Commander Ismo Siikaluma told Yle.
In Moscow Deputy Defense Minister Anatoly Antonov dismissed reports of Russian submarines allegedly prying into the territorial waters of European countries as an element of the information war being waged against Russia by the West.