However, the Swedish navy has said that it does not know exactly where the suspected Russian submarine is, and said the military can only speculate about its location. The military said its main task was not to sink the submarine, “but to find out what’s going on.”

Sweden says there have been three confirmed sightings of an unidentified foreign submarine in the waters of the Swedish archipelago over the past four days. At present, more than two hundred troops - on land, in helicopters and on ships - are involved in the search for the suspected Russian submarine.

Swedish intelligence sources say the submarine might be in difficulty, as they intercepted a distress call in Russian from the vessel.