Theresa May has launched a scathing attack on Russian President Vladimir Putin, accusing the Russian military of "sickening atrocities" in Aleppo, just hours before Moscow’s warships are due to pass through British waters.
The Prime Minister highlighted the "appalling" acts which have occurred during a sustained Russian bombing campaign that has pummelled the northern Syrian city.
As she spoke on arrival at her first EU summit as leader, a huge Russian naval taskforce was being shadowed by the Royal Navy as it headed towards the Mediterranean coast of Syria.
The Independent has been told the flotilla – including the nuclear-powered aircraft carrier the Admiral Kuznetsov – maintains current speed, it should enter the Channel before noon on Friday.
The EU is now considering threatening Moscow with sanctions over air strikes in Aleppo, according to a draft EU summit communique seen by the Guardian.
"The EU is considering all options, including further restrictive measures targeting individuals and entities supporting the regime, should the current atrocities continue," the draft reportedly says.
The heightened tension comes after a week of hand-wringing by Western powers about how to address the plight of Syrian civilians trapped in besieged Aleppo.
In Brussels, Ms May demanded a "robust and united European stance in the face of Russian aggression".
She added: "It is vital that we work together to continue to put pressure on Russia to stop these appalling atrocities, these sickening atrocities, in Syria."
Syrian forces, backed by Russian air power, have agreed a temporary humanitarian truce in Aleppo. Mr Putin has held out the prospect of extending it following a meeting with French President Francois Hollande and German Chancellor Angela Merkel.
Nato has said the prospect of Russia's fleet heading to the region does not "inspire confidence" that Moscow is seeking a political solution to the Syrian crisis.
An official for the alliance said: "Russia has the right to operate in international waters. There are plans in place for Nato navies to monitor the Russian ships as they head for the Mediterranean."
If the Russian warships stick to normal navigation rules for passing through the Dover Strait – which is likely since it is the world’s busiest seaway – they will use the shipping lane for south-west bound vessels, which is in UK territorial waters.
This will entail what one Russian newspaper has described as "the most powerful Russian naval task force to sail in northern Europe since 2014" passing within about 10 nautical miles (11.5 miles) of the British coast.
The Royal Navy has already sent one of its most advanced warships, the Type 45 destroyer HMS Duncan, along with the Type 23 frigate HMS Richmond to track the Russian vessels and "man-mark them every step of the way".
At the same time the Type 45 destroyer HMS Dragon has been sent south to shadow two Russian corvettes understood to be heading from the Atlantic near Portugal to link up with the Admiral Kuznetsov task force, which is said to be en route to support the assault on rebels in Aleppo.
A Ministry of Defence spokesman has promised: "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."
Before heading south west through the Dover Strait, most vessels are legally obliged to report to the UK’s Maritime Rescue Co-ordination Centre at Dover, which works with the French authorities to monitor ships going through the Channel and to report any traffic violations.
The Russian warships, however, will not have to formally notify the UK authorities of their intended movements, because naval vessels, whatever their nationality, are exempted from the reporting requirements. As matter of courtesy, however, most navies report to either Britain or France when their warships pass through the Channel.
The Admiral Kuznetsov, a 55,000-ton Soviet-era aircraft carrier, and seven other vessels are currently in international waters in the North Sea, having been seen off the coast of the Norwegian city of Bergen on Wednesday. Photos taken by Royal Navy photographers on board HMS Richmond suggest that they are already being closely shadowed.
HMS Duncan is thought to have left Portsmouth on Wednesday night in order to link up with HMS Richmond.
The Russian flotilla also includes the Pyotr Veliky (Peter the Great) battlecruiser and the anti-submarine vessel Severomorsk. A senior Nato diplomat told Reuters that the Russian warships are expected to sail through the English Channel, past Gibraltar and into the Mediterranean to arrive off the Syrian coast in about two weeks’ time.
The diplomat also suggested that the flotilla about to enter the Channel was part of a much bigger naval effort to reinforce Russia’s campaign to support the regime of Bashar al-Assad in Syria. The diplomat said: "They are deploying all of the northern fleet and much of the Baltic fleet in the largest surface deployment since the end of the Cold War.
"This is not a friendly port call. In two weeks, we will see a crescendo of air attacks on Aleppo as part of Russia's strategy to declare victory there. With this assault, it should be enough to allow a Russian exit strategy if Moscow believes Assad is now stable enough to survive."
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