THE WEST must prepare for a Russian nuclear doomsday by stockpiling anti-radiation drugs and building shelters, Ukraine's President has warned.

President Volodymyr Zelensky's chilling warning comes as Russia continues to amass its forces in eastern Ukraine ahead of a major battle tipped to decide to fate of the war.

The battle-hardened leader told CNN Vladimir Putin could use tactical nukes if his war in Ukraine continues to stall.

The deranged Russian leader ramped up his offensive on Ukraine after the flagship war vessel Moskva was downed on Thursday.

Putin's forces unleashed a wave of artillery attacks on eight towns including Kyiv, Kharkiv and Lviv.

And it comes as Kremlin spokesperson Dmitry Peskov told the US outlet that Moscow was prepared to use a nuclear weapon in Ukraine in the case of an "existential threat".

Live Ukraine war: Zelensky warns world ‘to prepare’ for Putin nuclear attack

Family of Brit captured in Ukraine furiously deny Russian claims he is a spy

President Zelensky told CNN on Friday: "We shouldn't wait for the moment when Russia decides to use nuclear weapons… We must prepare for that."

He said anti-radiation medicine and air raid shelters would be needed to repel the attack, which he was "convinced" was being planned.

"All of the world, all of the countries have to be worried because it can be not real information, but it can be truth," Ukraine's head of state said.

"Chemical weapons, they should do it, they could do it, for them the life of the people, nothing. That's why.

Most read in The Sun

DON'T RAIN ON ER PARADE

Harry & Meghan could 'hijack' Queen's Platinum Jubilee, royals fear

HOW MUCH?!

Mum-of-22 Sue Radford goes to waterpark & is stunned at how much cash kids spend

'COME ON ARCHIE'

Boy, 12, in coma after 'freak accident' at home leaving family heartbroken

PHIL'S A GAP

Man Utd boost in Phillips chase as Leeds line up Hoffenheim star Grillitsch

"We should think not be afraid, not be afraid but be ready. But that is not a question for Ukraine, not only for Ukraine but for all the world, I think."

CIA Director Bill Burns echoed Zelesky's concerns during a public appearance at Georgia Tech.

He said the intelligence body was watching Russia's nuclear movement "very intently", adding: "Given the potential desperation of President Putin and the Russian leadership, given the setbacks that they've faced so far militarily, none of us can take lightly the threat posed by a potential resort to tactical nuclear weapons or low yield nuclear weapons."

And Russian media pundits have outrageously claimed World War 3 has already begun.

Olga Skabeyeva, one of Putin's top media figures in the tightly controlled echo chamber of state-run Russian media, bizarrely claimed that war in Ukraine had escalated into a war against Nato.

Putin's propagandists are now desperately trying to distract from the tyrant's military failures in a war which was sold the Russian people as being a quick victory in a matter of days.

Military commentator Dmitry Drozdenko said on separate state-run Channel 1: “In actual fact a full-scale multi-level war is underway with the collective West.

“And the West has long been preparing for the war".

Russia is already using nuclear capable artillery guns in Ukraine stoking fears Putin may resort to using tactical nukes if his forces are repelled for a second time.

Putin's defence ministry stoked fears of turning the conflict nuclear as they released images of the massive 46.5 ton weapon firing shells towards Kharkiv in late March.