Officials believe it is Russian sub the Som (Catfish) which sank in 1916

Russian submarine found off Swedish coast thought to be old war vessel

A Russian submarine discovered by shipwreck hunters off the eastern coast of Sweden is believed to be a Tsarist vessel which sank after a collision with a ship during the First World War.

Swedish Armed Forces said the modern-looking vessel, with Cyrillic letters written on the hull, was likely to be Russian submarine the Som (Catfish) which collided with a Swedish ship in poor visibility, killing all 18 crew members, in 1916.

Speculation had been swirling about the origins of the vessel after Swedish divers announced yesterday that a shipwreck had been found about 1.5 nautical miles off the coast of Sweden.

The announcement came nine months after a high-profile hunt for a mystery submarine in Swedish waters, suspected to be Russian, and some speculated that the divers had chanced upon a modern Russian vessel.

The Swedish military however quashed rumours and said the vessel was old, referring to the design of the submarine and the lettering on the outer shell seen in the pictures of the wreck taken by the divers.

The military added that it did not think a full technical analysis was necessary.

Confirming the vessel's identity, a spokesman for the Swedish Armed Forces said: 'We are most likely talking about the Russian submarine the Som (Catfish) which sank after a collision with a Swedish vessel in 1916 during World War I and before the Russian revolution.'

Submarine expert Andrei Nikolayev described the find as 'very important for Russia'.

He said: 'This is clearly the Som, judging by its location and design.

'As they say, the war is not over until the last soldier has been buried.'

He said there were several theories as to why the submarine had sunk, adding that its commander was inexperienced.

'A lieutenant was in charge of our submarine,' he said.

Konstantin Bogdanov, head of a state-backed team of wreck divers in Russia, also said that the discovery appeared to be the Som, offering his team's help to study the find together with the Swedish divers.

'We are ready to conduct a joint expedition,' he said, stressing that it would be important to 'immortalise the memory' of those who perished.

SUBMARINE DELIVERED TO IMPERIAL RUSSIAN NAVY BEFORE FATAL SINKING The Russian submarine discovered by divers off the eastern coast of Sweden is believed to be a Som-class submarine. The Som (Catfish) was built in the United States in 1901 before being handed over to the Imperial Russian Navy in Vladivostok in 1904. It was then integrated into the Baltic Sea Fleet before later becoming a part of the Baltic Fleet in 1915. The Som (Catfish) was built in the United States in 1901 before being handed over to the Imperial Russian Navy in Vladivostok in 1904. It was then integrated into the Baltic Sea Fleet before the Baltic Fleet in 1915 The vessel, which measures around 66ft long (20 metres) and 11.5ft wide (3.5 metres), collided with a Swedish steam ship during the First World War on May 10, 1916, and sank. All 18 crew members on board the submarine at the time were killed in the incident, and the shipwreck lay undiscovered for more than a century. Officials were able to confirm its identity because of markings on part of the vessel's hull which included the letter 'yat' from the Cyrillic alphabet. 'Yat' was the thirty-second letter of the old Cyrillic alphabet, which was used in Russia before the 1917 Bolshevik Revolution. Advertisement

Hunt: This grainy amateur photo showing a mysterious vessel in Stockholm's archipelago was released by the Swedish military during the hunt in October last year

The discovery of the vessel comes less than a year after Sweden's military were engaged in an extensive hunt for a suspected Russian submarine.

The massive sea and air search took place in the Stockholm archipelago in October.

At the time it was described as the country's biggest military mobilisation since the Cold War, but it was called off after a week.

Moscow always denied that any of its vessels were in Swedish waters.

Ocean X Team, the company behind the discovery, said on its website: 'It is unclear how old the submarine is and for how long it has been at the bottom of the sea, but the Cyrillic letters on the hull indicate that it is Russian.'

They said the vessel was around 20 metres (66ft) long and 3.5 metres wide.

Dennis Asberg, a partner in Ocean X Team, added: 'I am 99.9 percent sure it's from 1916, but the next step is to go down again and confirm it.'

Fellow diver Stefan Hogeborn said it remained 'completely intact' with 'no visible damage' and the hatches closed.

Mr Hogeborn was quoted as saying he feared the crew had not been able to escape when the vessel went down.

War games? A Swedish minesweeper and a guard boat in Namdo Bay searching for the mysetry Russian submarine last year

Concerns about possible incursions by Russian submarines have increased as relations between Moscow and the West have worsened due to events in Ukraine.

During the Cold War, the navy repeatedly chased suspected Soviet submarines along its coast with depth charges.

In 1981, in an incident known as 'Whiskey on the Rocks,' a Soviet nuclear Whiskey-class submarine was stranded near a naval base deep inside Swedish waters after it ran aground, causing a diplomatic standoff.

There have been many false alarms.

In 1995, then-Prime Minister Ingvar Carlsson said the military on several occasions thought it had detected submarines only to find many of the underwater sounds were made by minks.