NATO Secretary-General Mark Rutte said Friday that the military alliance will step up patrols in the Baltic Sea region as Finnish investigators work to establish whether a ship linked to Russia sabotaged undersea cables there this week.

This latest episode of cable damage adds to a series of similar disruptions or suspected sabotage acts in the strategically important Baltic Sea.

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.