A Royal Navy frigate is escorting four Russian naval ships through the English Channel.
HMS Westminster is accompanying two Russian frigates and two support ships as they head north returning from the Mediterranean.
Naval sources said the contact was routine, but it comes amid an estimated 10-fold increase of Russian naval activity in waters around Britain and in the North Atlantic this decade.
Commander Simon Kelly, the Commanding Officer of HMS Westminster, said: "HMS Westminster's role as the Royal Navy's Fleet Ready Escort is to be at very high readiness to respond to anything the British government requires.
"While today most people are returning to work for the first time in the New Year, HMS Westminster's ship's company has been at sea and at readiness as part of the Royal Navy's commitment to keep Britain safe at all times.
"The English Channel is an absolute lifeline for the UK, and it is very important HMS Westminster and the Royal Navy maintains a watchful eye on this key strategic link."
Activity has risen in recent years with warships passing Britain on their way to join Russia's military campaign to prop up Bashar al-Assad in Syria.
On Christmas Day, the frigate HMS St Albans was dispatched to track the Russian vessel Admiral Gorshkov as it made its way through the North Sea close to Britain.
And on Christmas Eve, HMS Tyne was dispatched to escort a Russian intelligence-gathering ship through the North Sea and the England Channel.
A Wildcat helicopter was then also dispatched to monitor two further Russian vessels.
Royal Navy's HMS Westminster
Giving a strong statement last month, Defence Secretary Gavin Williamson, said: "I will not hesitate in defending our waters or tolerate any form of aggression.
"Britain will never be intimidated when it comes to protecting our country, our people, and our national interests."