Soviet Sub Found
The wreck is believed to be that of the S-6, which disappeared in September 1941.
"In the autumn of 1941 several Russian submarines left their home bases to patrol the Baltic Sea. Several of them never returned. One of them has now been found, blown up into large pieces, southeast of Oeland," the armed forces said in a statement.
The S-6 was probably blown apart by a German mine, though the military said it was impossible to say for certain what had happened.
The vessel was found in international waters in Sweden's economic zone, in a heavily-mined area known as the "Wartburg minefield".
Initially located by a Swedish team of civilian divers several months ago, the discovery has been confirmed by a navy ship specialised in submarine rescues.
In June 2009, divers found the wreck of the S-2, another Soviet sub sunk by mines in January 1940 with some 50 crew members on board, in waters further north between Sweden and Finland.