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

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 lines, while alliance member Estonia launched a naval operation to guard a parallel electricity link.

STORY: The seized oil tanker accused of sabotaging an undersea power cable and four internet cables now sits off Finland's coast.Finnish investigators said the ship that has been linked to Russia may have caused damage to the cables by dragging its anchor along the seabed,