Estonia has begun naval patrols to protect an undersea cable supplying electricity from Finland following suspected sabotage of another one on Christmas Day, Defense Minister Hanno Pevkur said Friday.

Finland’s prime minister says authorities are investigating an interruption in a power cable under the Baltic Sea between his country and Estonia.

Finland has seized an oil tanker suspected of having severed undersea power and internet cables, with Finnish authorities saying the vessel may have been part of Russia's "shadow fleet" of ships aimed at skirting Western sanctions.