STOCKHOLM (Reuters) - The Swedish military is studying a video taken by shipwreck hunters who say it shows a wrecked submarine just off the eastern coast of Sweden which appears to be Russian, a spokesman said on Monday.

The discovery comes less than a year after Swedish troops and ships unsuccessfully hunted for a Russian submarine reportedly cited near Stockholm, in the country's biggest military mobilization since the Cold War.

Swedish Armed Forces spokesman Anders Kallin did not say whether the military also believed it was a Russian submarine.

"We choose not to comment on it before we have seen more material. We will continue the analysis together with the company in the coming days," Kallin said.

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."

One of the men who discovered the submarine, Dennis Asberg, told the Expressen newspaper it looked modern. But one expert quoted by the paper said he believed it was a Russian submarine that sank in 1916.

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.

In April, the Finnish military used handheld underwater depth charges as a warning against what it suspected was a submarine in waters off Helsinki.

(Reporting by Sven Nordenstam; Editing by Alistair Scrutton and Robin Pomeroy)