Video footage by a group of salvage hunters purporting to show a wrecked underwater vessel in Swedish waters is likely that of a Russian so-called 'Som class' submarine (nicknamed 'Catfish') which sank in May 1916, an analysis by the Swedish Armed Forces suggested on Tuesday afternoon.
"It was found outside the coast of Uppland (a region in central Sweden just north of Stockholm) and according to the video material it is a Russian 'Som' submarine, which sank after it collided with a Swedish vessel in 1916," press spokesman Jesper Tengroth told The Local.
The submarine was built for the Imperial Russian Navy in Vladivostok in 1904 and integrated into the naval fleet in the Baltic Sea in 1915. It ran aground with an 18-member crew a year later.
The video footage was handed over to the Armed Forces by salvage hunters Ocean X Team. The company said they made the discovery last week, although it only became known to the public yesterday.
"We won't take this forward with a technical analysis, because there is no military interest any more. We have done our bit and have reported it to the government. They will take it further and then they have to agree with Russia about what to do," said Tengroth.
According to Stefan Hogeborn, a diver from the Ocean X Team, the vessel, which is carrying Cyrillic letters, was “completely intact” with “no visible damage to the hull” and the hatches closed, which he said could indicate the crew was still inside.
He did not give the vessel's location but according to Swedish tabloid Expressen, which published images of the wreck on its website, it was found about 1.5 nautical miles (2.8 kilometres) off the east coast of central Sweden.
Ocean X Team said the vessel was around 20 metres (66ft) long and 3.5 metres wide.
Earlier in the day, government-owned Russian news site Sputnik News launched a verbal attack on Sweden, saying that "the paranoia has not ceased". "Here we go again..." said the scathing article, referring to last year's submarine hunt in the Stockholm archipelago.
"It was expected that they would respond in this way. If the submarine is shown to be historical the Russians will mock Sweden even more," Tomas Ries, senior lecturer at the Swedish Defence University (Försvarshögskolan), predicted in an interview with The Local earlier on Tuesday.
In October last year, Sweden's navy launched a massive hunt for a foreign submarine, suspected to be Russian, in the Stockholm archipelago.
The military subsequently confirmed that “a mini-submarine” had violated its territorial waters, but was never able to establish the vessel's nationality.
During the Cold War the Swedish Navy repeatedly chased suspected Russian submarines along its east coast. A 1981 incident known as “Whiskey on the rocks” saw a Soviet nuclear Whiskey-class submarine stranded far into Swedish waters after it ran aground, sparking a diplomatic standoff.
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Meanwhile, Ocean X Team said it was planning a new expedition to examine the wreck more closely.
We only speculate now, it may be an older submarine yes true, but there's only one way to know, and that is to examine it with the divers- Ocean x Team (@OceanXteam) July 27, 2015
The Local has sought a comment from Sweden's Foreign Ministry.
Additional research by Elin Jönsson.