Portsmouth-based Royal Navy destroyers have been sent to meet a Russian aircraft carrier and other Russian warships heading towards the English Channel.
It is understood a task force including the carrier Admiral Kuznetsov is on a course to sail through the North Sea and then the English Channel.
Two other Russian corvettes, which are travelling north towards the UK from Portugal, are also set to be watched by the navy.
A Ministry of Defence spokesman said: ‘When these ships near our waters we will man-mark them every step of the way.
‘We will be watching as part of our steadfast commitment to keep Britain safe.’
Warship HMS Duncan sailed from Portsmouth on Tuesday to monitor the Kuznetsov task group, which is heading south from the Norwegian Sea towards the North Sea.
HMS Richmond has also escorted the group in the Norwegian Sea further north of the UK between Iceland and Norway.
And HMS Dragon is also due to sail to meet two Russian corvettes travelling north towards the UK from the direction of Portugal.
It is understood that shadowing ships is regular business for the Royal Navy, which has been supported by Royal Air Force surveillance aircraft this time.
Navy ships will continue to escort the Russian task group and provide a visible presence south through the North Sea and English Channel as the Russian fleet sail through and carry out their flying operations, the MoD said.
The UK is working alongside Nato partners to monitor the warships passing the UK this week.
Last month HMS Tyne twice escorted Russian warships through the Channel.