Russia's unconventional attacks against NATO "look like war" and allies must set new red lines that will trigger a retaliation if crossed, a former foreign minister has warned.

NATO Deputy Assistant Secretary General James Appathurai has issued a warning about Russia’s increasing hybrid warfare tactics amid fears of an escalation in its war with Ukraine.

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.

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