VITALI Klitschko has voiced concerns that Russia could nuke Kyiv amid fears the world is teetering on the edge of a "fully fledged" nuclear war.
The heavyweight boxer turned mayor of the Ukrainian capital is "worried" mad Vlad will pull out the big guns as his invasion falters.
The Russian despot could launch a desperate attack on Kyiv after his henchmen abandoned their attempts to seize the key city.
Despite the trail of devastation left in their wake, brave Ukrainians have begun to rebuild their lives - but Klitschko has warned residents they are returning "at their own risk".
The mayor told CNN: "As the leader of Kyiv, I tell everyone, 'I'm sorry, it's your personal risk, but we can't give you guarantees.'
"While Ukraine is at war, we can't give guarantees to any Ukrainian."
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He doubled down on his predictions that Putin's main plot is to occupy the city, saying he had "no doubt" it was still in his sights.
And he fears he will stop at nothing - even nuclear warfare - to achieve his goal, saying an attack could come at "any minute".
It comes as a former Kremlin president - who had had his finger on the Russian nuclear button - warned that the world is on the brink of an atomic war.
Dmitry Medvedev, a close ally of Vladimir Putin, called on the West to pull back from supplying arms to Ukraine.
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The politician, who was Russian president from 2008 to 2012, wrote: "The endless talk by foreign analysts about a war between NATO and Russia continues unabated.
"The cynicism of Western ‘talking heads’ is becoming more and more blatant.
"The thesis that Russia frightens the world with a nuclear conflict is being pushed to the top of the agenda.
"Even [Donald] Trump recently came out with this, though, understandably, just to spite [Joe] Biden.
"And of course the Europeans are squeaking their little voices."
He continued: "In the context of the proxy war with Russia unleashed by the Western countries, I want to articulate very clearly once again the things that are so obvious to all reasonable people.
"One, the pumping of Ukraine with weapons by NATO countries, the preparation of its troops to use Western equipment, the sending of mercenaries and the conduct of exercises by Alliance countries near our borders increases the likelihood of a direct and open conflict between NATO and Russia instead of the 'proxy war' they are waging.
A WARNING TO THE WEST
"Two, such a conflict always has a risk of escalating into a full-fledged nuclear war.
“Three, this would be a catastrophic scenario for all. That’s it.
"So you don't have to lie to yourself and others. You just have to think about the possible consequences of your actions.
"And don't choke on your own saliva in paroxysms of Russophobia."
Medvedev, 56, is now Putin’s deputy on the powerful Russian national security council.
He is one of three men alive whose finger has been on the Moscow nuclear button.
The other two are Putin and ex-Soviet leader Mikhail Gorbachev.
Medvedev was Putin's prime minister and then became president from 2008 to 2012 - with Putin as his PM in a bizarre job swap.
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Putin was forced to step aside from the top job because of rules limiting how long he could serve, but observers believed he was still really the one in charge.
He has since changed Russia's constitution so he can stay on as president until 2036.