Under steel grey skies, the Dutch minehunting vessel Schiedam cuts through the waters dividing Denmark and Sweden, part of NATO's Baltic Sentry mission to protect underwater infrastructure in the Baltic Sea.

At a time when the eight NATO nations bordering the Baltic Sea are on high alert after a string of undersea power and internet cables were suspiciously severed, Russia's shadow fleet is getting extra attention.

The European Union and NATO must strengthen cooperation to protect critical energy infrastructure from attacks, which pose a growing threat to European stability. The Kremlin, with its history of weaponizing energy,

Estonia's navy is prepared to act against vessels that pose a danger to Baltic Sea infrastructure even if they are in international waters, a senior official patrolling the busy Gulf of Finland shipping lane said on Thursday.

NATO and its eight Baltic Sea allies say they are stepping up efforts to deter 'any attempts at sabotage' in the wake of a series of incidents that have damaged key undersea power and telecommunications cables.