Royal Navy vessels are following Russian warships as they pass through the English Channel on their way to the eastern Mediterranean to a suspected bolstering of the bombing campaign of Aleppo.
The Russian fleet will be marked "every inch of the way", according to Defence Secretary Sir Michael Fallon as he claimed the deployment was aimed at testing British capabilities.
The Russian vessels, including the aircraft carrier Admiral Kuznetsov, were being shadowed by the Navy as they headed towards Syria via the Dover Strait.
The Admiral Kuznetsov is the only carrier in the Russian navy and can carry more than 50 aircraft. Its weapons systems include granit anti-ship cruise missiles.
On Tuesday, Type 45 destroyer HMS Duncan sailed from Portsmouth to "man-mark" the Kuznetsov group, and Type 23 frigate HMS Richmond escorted the group from the Norwegian Sea as it steamed south.
The Russian deployment comes as Theresa May condemned President Vladimir Putin's aggression in Syria, accusing Moscow of being behind "sickening atrocities" in support of Bashar Assad's regime.
Syrian forces, backed by Russian air power, have agreed a temporary humanitarian truce in Aleppo, but Ms May has urged European leaders to take a firm stance against Moscow.
The former UK Ambassador to Russia from 2004 to 2008 Sir Anthony Brenton said he believes Russia is angry after the ceasefire talks in Syria failed and they are worried about how the West will react.
Sir Brenton said: "They're putting on a very firm demonstration of their determination not to be pushed around by the West in Syria which includes their current military maneuvers.
"Fundamentally a signal to the West that they're not going to back down."
Nato said the prospect of Russia's only aircraft carrier heading to the region does not "inspire confidence" that Moscow is seeking a political solution to the Syrian crisis.
Russia already has around 10 ships off the coast of Syria. In the past they have fired cruise missiles during Russia's bombardment of what it says are anti-government rebels in Syria.