Finnish investigators probing the damage to a Baltic Sea power cable and several data cables said they found an anchor drag mark on the seabed, apparently from a Russia-linked vessel that has already been seized.

Finnish police said on Sunday they had found tracks that drag on for dozens of kilometres along the bottom of the Baltic Sea where a tanker carrying Russian oil is suspected of breaking a power line and four telecoms cables with its anchor.

Finland has seized the Eagle S, a Cook Islands-flagged oil tanker, as part of an investigation into severe damage to underwater cables in the Baltic Sea.

General Mark Rutte says the military alliance will step up patrols in the Baltic Sea area as Finnish investigators work to establish whether a ship linked to Russia sabotaged undersea cables there this week.

NATO said on Friday it would boost its presence in the Baltic Sea after the suspected sabotage this week of an undersea power cable and four internet cables, while alliance member Estonia launched a naval operation to guard a parallel electricity link.

This photo provided by Rajavartiosto (Finnish Border Guard) on Thursday, 26 Dec 2024, shows the oil tanker Eagle S, background, and the Finnish Border Guard ship Turva.

Police and media reports say that Finnish authorities have detained a Russia-linked ship as they investigate whether it damaged a Baltic Sea power cable and several data cables.

Baltic Sea countries have been on high alert after a string of outages of power cables, telecom links and gas pipelines since Russia invaded Ukraine in 2022