Sweden says a submarine wreck found last week in its territorial waters was most likely Russian World War I submarine the Som, which sank after colliding with a Swedish ship in 1916.

Swedish Armed Forces spokesman Jesper Tengroth says investigators on Tuesday analyzed video footage provided by the diving company that found the wreck.

Tengroth told The Associated Press they had reported the results of their investigation to the Defense Ministry and that "now it's a diplomatic question between Sweden and Russia."

The find follows a lengthy hunt for a foreign submarine in Swedish waters in October during a period of growing military activity in the Baltic Sea region, with several reports of airspace violations by Russian military aircraft and an increased presence of Russian military vessels.