The Swedish military is examining footage which appears to show the wreckage of an abandoned Russian submarine.

Shipwreck hunters from the Ocean X Team are unsure how long what appears to be a 20m long vessel has been lying on the seabed in Swedish territorial waters.

But they claimed "Cyrillic letters on the hull indicate that it is Russian".

Swedish Armed Forces spokesman Jesper Tengroth said there was no hurry to investigate "because the wreck was not going anywhere", adding it is better "to come back with facts rather than speculation".

Ocean X is planning a new expedition to examine the shipwreck more closely.

On its website, it said: "It is unclear how old the submarine is and for how long it has been at the bottom of the sea.

"The submarine is completely intact, has no visible damage to the hull, and the hatches are closed. Therefore, we do fear that the crew would not have been able to save themselves when the sub went down."

Although one of the men involved in discovering the submarine has claimed the vessel looked modern, an expert told the Expressen newspaper that he believed it was a Russian wreck dating back to 1916.

Less than a year ago, the navy said it had detected an underwater intruder - believed to be a Russian submarine - in Sweden's territorial waters.

This prompted the country's largest military mobilisation since the Cold War, but the hunt proved unsuccessful.

There have been several false alarms regarding suspected foreign submarines in Sweden over the years.

One of the most notable incidents was in 1995, when the Swedish military believed it had detected intruders in its territorial waters several times.

However, they were embarrassed to learn that many of the underwater sounds collected as evidence had been made by minks, a small animal from the weasel family.