People have been gathering on the cliffs of Dover as Russian warships pass through through to reinforce the attack on the besieged city of Aleppo.
The Admiral Kuznetsov and seven other vessels are passing the UK as they head to Syria, where Russia backs the regime of President Bashar al-Assad.
The Royal Navy said it and Nato would monitor the mission, as is usual when other nations' fleets enter UK waters.
A Navy spokeswoman said: "UK and Nato assets routinely monitor warships from other nations when they enter our area of interest and this will be no different."
Two British naval ships are shadowing the Russian vessels.