A British Navy warship was called into action on Christmas day to escort a Russian vessel which was near UK waters in the North Sea.
"Russia's submarine activity is now at its highest level since the Cold War."
NATO Secretary General
The HMS St Albans - a so called high-readiness unit - was sent to patrol the area after the Admiral Gorshkov came close to entering UK territory.
Britain has previously reported Russia poses a threat to underwater internet cables.
In an interview, NATO Secretary General Jens Stoltenberg has warned of Russia expanding it's naval operation saying;
"Russia's submarine activity is now at its highest level since the Cold War."
Britain has been working in partnership with NATO aircraft to monitor any threat in the North Atlantic.
