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

NATO has said it will enhance its military presence in the Baltic Sea after undersea power and internet cables were cut between Estonia and Finland. The bloc's secretary general Mark Rutte said he had spoken to Finland's President Alexander Stubb about the "possible sabotage", adding: "NATO will enhance its military presence in the Baltic Sea".