Swedish and Finnish Navy units kicked off the annual Swefinex exercise in waters around Swedish Gotland Island.
The exercise, which is this time hosted by Sweden, started May 16 and will last until May 26.
Participating units will be conducting anti-submarine warfare, mine clearance drills and practice merchant vessels escort tasks.
Swefinex is part of an undertaking to have a Swedish-Finnish Naval Task Group (SFNTG) ready for operations by 2017. The SFNTG would then be deployed to deployments in the Arctic and conduct exercises and sea surveillance.
In the autumn of 2013, Sweden and Finland announced their intent to deepen their defence cooperation. The aim was to improve security in a regional context and Russia in hindsight.
Sweden is deploying 600 soldiers while Finland will have around 250. Submarines, mine clearing and support vessels and helicopters, reconnaissance and fighter planes will practice hunting submarines during the 10-day exercise.