Vladimir Putin will "destroy the world" if left unchecked and global leaders should brace for Russia to deploy nuclear weapons, an opposition politician has said.
Leonid Volkov, the former chief of staff for jailed Putin critic Alexei Navalny, issued a chilling warning over the Kremlin's plans and said he wanted his fellow Russians to make it clear it was "not our war".
Prominent opposition leader Mr Navalny, who has accused Putin of corruption, was poisoned by the novichok nerve agent in 2020 and later imprisoned on his return to Russia in 2021.
Mr Volkov said Putin was "crazy enough" to use nuclear weapons as the conflict in Ukraine continues to escalate.
He told Sky News' Sophy Ridge on Sunday: "It is now very clear that enormous cost has to be paid to stop this war.
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"There are all the sanctions, of course, they also create a burden on the European economy that is quite clear.
"But this cost has to be paid because otherwise Putin will just destroy the world."
Asked if Putin would use nuclear weapons, Mr Volkov replied: "As he is crazy enough, we can expect unfortunately everything."
He had earlier said the war feels "enormously painful", adding: "I want to cry. Putin is president of Russia. This is Putin's war, not my war.
"I am trying to cry as loud as possible and I ask my fellow compatriots to cry.
"This is not our war, not in our name. He is doing it. Not in our name."
Meanwhile, Poland's President warned Moscow could use “anything” including chemical weapons.
Andrzej Duda told the BBC 's Sunday Morning: “This is something that the world has not seen on this scale since the Second World War.
“If you’re asking can Putin use chemical weapons, I think that Putin can use anything right now, especially because he’s in a very difficult situation.”
Fears are mounting that Russia is paving the way for a "false flag" attack by blaming Ukraine for using chemical weapons before launching its own.
Top Tory Michael Gove said Putin was capable of "terrible, terrible violence" but he refused to specify how the UK would respond to a chemical attack on Ukraine.
But Mr Gove said it was not helpful to describe the Russian President as "mad".
"I think he's operating according to a set of criteria totally detached from those which you or I would consider to be reasonable or rational," he said.
"But, yes, I don't think it's helpful to think of Putin as mad.
"I think what we do need to think of him as, and indeed we do need to recognise, is someone whose ruthlessness takes them into a moral sphere that the rest of us would find almost impossible to conceive of."
Labour leader Keir Starmer said it was clear Russia had committed war crimes in Ukraine.
He told Sky: "What I have seen already amounts to war crimes. Particularly the awful attacks on civilians.
"I think it is very important he is held to account and is responsible, and all those that are acting with him know that they too will be held to account.
"This is something which we need to make clear now so that those who are involved at the moment know what the consequences are."
Asked if Nato should do more in the event that Russia uses chemical weapons, he said the UK "shouldn't be speculating" during the conflict, but should work "in lockstep" with allies.
