Nations on the Baltic Sea, along with NATO, have stepped up security after a third incident of suspected sabotage to underwater infrastructure in a month.

The Eagle S, thought to be part of Russia’s “shadow fleet,” was detained in December following suspected sabotage.

NATO is deploying approximately 10 ships to protect underwater infrastructure in the Baltic Sea. The first of these ships is expected to arrive by the end of the week, and the operation will continue until April.

Finnish President Alexander Stubb will host a summit in Helsinki of the NATO countries that border the Baltic Sea together with Estonian Prime Minister Kristen Michal next Tuesday. The summit, which will take place at the Presidential Palace,

NATO ships will start guarding critical locations in the Baltic Sea later this week, Finnish public broadcaster YLE reported on Wednesday.