The European commission has announced it is stockpiling equipment and medicines in preparation for a chemical or nuclear attack.
Vladimir Putin put Russia's nuclear forces on "high alert" in the first week of his invasion of Ukraine, raising the spectre of nuclear war to levels not seen since the Cold War.
Now the European Commission has said it is building a €540million emergency stockpile of “equipment and medicines, vaccines and other therapeutics” to treat patients exposed to chemical, biological, radiological and nuclear emergencies.
The fund will also cover expert response teams who can be deployed in case of emergencies.
The commissions's spokesperson for crisis management, Balazs Ujvari, told reporters on Wednesday: "First of all, there is a rescue strategic stockpile with over 540 million euros, which will be developed through the EU civil protection mechanism.
"This will comprise response equipment and medicines, vaccines and other therapeutics to treat patients exposed to CBRN [chemical, biological, radiological and nuclear] emergencies.
"Secondly, a rescue decontamination reserve will be set up to provide decontamination equipment and expert response teams in an event of an emergency.
"As an immediate first step, the EU has already mobilised its rescue medical reserve to replenish stocks of potassium, iodine tablets to protect people from the harmful effects of radiations."
The Kremlin has raised the prospect of pressing the nuclear button, with Putin's spokesperson Dmitry Peskov, refusing to rule out the use of nuclear weapons if Russia was faced with an "existential threat".
Two weeks ago, Dmitry Polyanskiy, the Russian deputy ambassador to the UN, warning Moscow reserved the right to deploy nuclear weapons if "provoked".
Asked if Putin was right to hold the prospect of nuclear war over the rest of the world, Polyanskiy told Sky News: "If Russia is provoked by Nato, if Russia is attacked by Nato, why not, we are a nuclear power.
"I don’t think it’s the right thing to be saying. But it’s not the right thing to threaten Russia, and to try to interfere.
"So when you’re dealing with a nuclear power, of course, you have to calculate all the possible outcomes of your behaviour."
Fears of a nuclear disaster were stoked after Russian troops took over Chernobyl nuclear station.
Ukrainian officials claimed this week the soldiers fled with radiation sickness after digging into contaminated soil.
In March, Putin's forces began shelling Europe’s largest nuclear power plant - Zaporizhzhia - as part of its assault on Ukraine.
Watch: Luhansk could be 'even worse' than Mariupol as Russian attacks increase
Of the nine countries that possess nuclear weapons, Russia is believed to have the most.
The Federation of American Scientists (FAS), which compiles the list of the world’s nuclear weapons, says Russia has a total inventory of 5,977 nuclear warheads. This includes stockpiled and retired warheads.
Of that figure, 1,588 are deployed strategic warheads on ballistic missiles and at bomber bases.
Another 2,889 of Russia’s warheads are non-deployed or reserve weapons. Added together, this gives a military stockpile total of 4,477 nuclear warheads.
It comes as Russia faces accusations of war crimes in Ukraine, with reports emerging of mass killings, rape and torture being perpetrated by Russian soldiers.
Russia has refuted claims of mass killings since Bucha, a town just outside of Kyiv, was freed from their control on 31 March, with Russian foreign minister Sergei Lavrov claiming footage and images of bodies in the streets were "staged" and Ukrainians had used "fake dead bodies".
However, satellite imagery of the area in the days before Bucha was freed shows at least nine bodies lying in the street for weeks, contradicting Russian claims.