Royal Navy warship HMS Argyll has been tasked with monitoring two Russian naval ships that have headed through the English Channel.
Tensions remain strained over Russia's build-up of troops on the Ukraine border as Boris Johnson also met with Ukrainian president Volodymyr Zelensky amid what the pair described as "ongoing Russian aggression".
The French military tweeted on Monday that it had monitored two Russian ships – the Soobrazitelniy and the Stoykiy – before handing over the responsibility to Type 23 frigate HMS Argyll and the US Navy's USS Roosevelt.
A Ministry of Defence (MOD) spokesperson described the tasking as a "normal response", adding: "As part of a unified response with our allies, the Royal Navy monitor the presence of Russian naval ships as they transit through the English Channel."
Russia's state news agency Tass reported on 24 January that the two Russian vessels had left Kaliningrad to conduct "combat exercises".
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A joint statement issued following Mr Johnson's meeting with Mr Zelensky outlined how the UK stands "shoulder to shoulder with Ukraine in the face of ongoing Russian aggression".
The statement, released by the offices of the Prime Minister and the president, said: "The Prime Minister emphasised the United Kingdom's unwavering commitment to Ukraine's sovereignty, independence, and territorial integrity within its internationally recognised borders."
At a joint press conference with the Ukrainian president, Mr Johnson warned Russia that the United Kingdom will hit Moscow with sanctions the "moment the first Russian toecap crosses further into Ukrainian territory".