The UK is advising all British nationals whose presence in Russia is not essential to consider leaving.
In updated advice, the Foreign Office says people should leave Russia by remaining commercial routes.
The government had already advised people not to travel to Russia “due to the lack of available flight options to return to the UK and the increased volatility in the Russian economy”.
The warning includes a note about Moscow imposing severe restrictions on the publishing and distribution of information relating to Russia’s armed forces and military operations.
It adds: “If you are in Russia, you should be aware that it may not be possible to fly directly to the UK, or via EU countries, and should amend any travel plans accordingly.”