The undersea power cable linking Finland and Estonia was damaged on December 25 along with four telecoms lines. Finnish authorities boarded the tanker the following day on suspicion it had caused the damage by dragging its anchor along the seabed.

Baltic Sea nations are on high alert after a string of outages of power cables, telecom links and gas pipelines since Russia invaded Ukraine in 2022. NATO said last week it would boost its presence in the region.

Fingrid said in a statement it had asked the Helsinki District Court to formally seize the Eagle S to help secure its financial claim.

“Further investigations at the damage site are expected to provide more information about the extent of the damages and enable more detailed planning and scheduling of the repair,” Fingrid said.

The owner of the ship, United Arab Emirates-based Caravella, has previously asked that Finnish authorities release the vessel.

Finland's customs service has said it believes the Eagle S is part of a shadow fleet of tankers used to circumvent sanctions on Russian oil, and has formally impounded its cargo although this is still on board the ship.