Western powers have begun to withdraw some of their staff from embassies in Kiev amid fears that an invasion by Russia of Ukraine is imminent.
About half of those working in the UK's mission to Kiev are to return to Britain. On Sunday, the US State Department announced it was ordering diplomats' family members to leave Ukraine. Its embassy in Kiev said “military action by Russia could come at any time".
The Australian government has "directed the departure" of dependants of its embassy staff from Kiev and urged its citizens to leave Ukraine, warning that "security conditions can change at short notice".
"If you're in Ukraine, you should leave now by commercial means if it's safe to do so. Flight availability could change or be suspended at short notice. Contact airlines or transport providers directly," said its travel advice and consular information service.
The UK Foreign Office said on Monday some staff and dependants were being withdrawn in response to “a growing threat from Russia".
“The British embassy remains open and will continue to carry out essential work,” it said on Twitter.
Russia has massed about 100,000 troops on its border with Ukraine but rejects claims it is set to carry out an invasion.
Current UK government advice warns citizens against all travel to the Donetsk, Luhansk and Crimea regions, and all but essential travel to the rest of Ukraine.
“The situation in Kiev and other areas outside Donetsk and Luhansk is generally calm. However, events in Ukraine are fast moving. There is continuing uncertainty about Russian intentions. Non-essential travel is advised against. Make sure you are ready to change your plans quickly if you need to,” was the government's advice.
UK Prime Minister Boris Johnson said an invasion by Russia "could be a new Chechnya".
"Invading Ukraine, from a Russian perspective, is going to be a painful, violent and bloody business," he said.
Referring to the US announcement, the Ukrainian Foreign Ministry said it considered the move to be “premature and a manifestation of excessive caution”.
“In fact, there have been no cardinal changes in the security situation recently: the threat of new waves of Russian aggression has remained constant since 2014 and the build-up of Russian troops near the state border began in April last year,” it said.
However, the EU does not plan to withdraw diplomats' families from Ukraine for now, the bloc's foreign policy chief Josep Borrell said on Monday.
“We are not going to do the same thing because we don't know any specific reasons,” he said.
Mr Borrell said that Antony Blinken, the US Secretary of State, would “inform us”, as he arrived in Brussels for a meeting with EU foreign ministers that Mr Blinken is expected to join in virtually.
UK Foreign Secretary Liz Truss, meanwhile, has accused Russia of seeking to install a pro-Moscow leader as head of the Ukrainian government. Russia has rejected the claim.
"The reason we put that out into the public domain is we are going to call out every instance of Russia trying to influence democracy, trying to subvert Ukraine, false flag operations and sabotage," Mr Truss said in Brussels on MOnday.
The Russian Foreign Ministry described the claims as "disinformation", accusing Britain and Nato of "escalating tensions" over Ukraine.
Deputy Prime Minister Dominic Raab on Sunday said there was a “very significant risk” of Russia invading its neighbour.
“The world needs to keep its eye on this and be very clear with President Putin that it would not do this cost-free, that there would be a price,” he told the BBC.
“A price in terms of the strenuous defence that we would expect the Ukrainians to put up but also the economic cost through sanctions, which are of course more effective if the international community speaks as one or at least with a broad consensus.”