It is being seen primarily as a warning to the West to discourage it from continuing to help Ukraine fight back against Russia, by providing investment and weapons.
The threat, understandably, has put many members of the public on edge. But just how seriously should we take these threats?
What exactly is the threat?
Putin has claimed that the West is threatening “nuclear blackmail” itself by alleging representatives of Nato (the North Atlantic Treaty Organisation) have considered using nuclear weapons against Russia.
He warned in response that Russia “has various weapons of destruction and with regards to certain components they’re even more modern than Nato ones”.
“If there is a threat to the territorial integrity of our country, and for protecting our people, we will certainly use all the means available to us – and I’m not bluffing.”
Plenty of Putin’s supporters are echoing his claims. For instance, his former advisor Sergei Markov also threatened nuclear war against the UK during an interview with BBC Radio 4′s Today programme on Wednesday.
How worried are Western leaders?
Some people are not alarmed, especially as Putin has been making similar threats since the start of the war.
In response to these claims, Ukrainian president Volodymyr Zelenskyy said:
“I don’t believe that he will use these weapons. I don’t think the world will allow him to use these weapons.”
Ukraine’s foreign minister Dmytro Kuleba also seemed undeterred by the threats. He said: “The Russians can do whatever they want. It will not change anything.”
Ben Wallace, defence secretary, tweeted on Wednesday that “no amount of threats and propaganda can hide the fact that Ukraine is winning this war”.
Foreign office minister Gillian Keegan took a more cautious line on Sky News, noting the threat was to be taken “very seriously”, and “obviously an escalation” of tensions.
Dutch prime minister Mark Rutte recommended people “remain calm”, noting: “His rhetoric on nuclear weapons is something we have heard many times before, and it leaves us cold.”
German chancellor Olaf Scholz tweeted: “Russia cannot win this criminal war. Right from the start, Putin completely underestimated the situation – the will to resist of Ukraine and the unity of their friends.”
The UN’s secretary general Jens Stoltenerg admitted it was a “dangerous and reckless” threat from Moscow, but added: “He knows very well that a nuclear war should never be fought and cannot be won, and it will have unprecedented consequences for Russia.”
The US is also taking the “irresponsible” threat to use nuclear weapons “seriously”, according to John Kirby, spokesman for the White House’s National Security Council.
“It’s irresponsible rhetoric for nuclear power to talk that way. But it’s not atypical for how he’s been talking the last seven months and we take it very seriously.”
He added: “We’re monitoring as best we can – their strategic posture. So if we have to, we can alter ours. We’ve seen no indication that that’s required right now.”
What do experts say?
Experts seem divided in how to respond to Putin’s claims – especially as he has been trying to use his nuclear power as leverage since the start of the war.
Defence expert General Sir Richard Barrons told Sky News on Wednesday that the threats have great significance for the West – even though Europe and its allies have been trying to avoid direct intervention in the war.
He said: “Essentially, by raising the spectre of nuclear weapons, the rest of the Western hemisphere is now on the pitch with Ukraine.”
But, former British ambassador to Russia, Sir Laurie Bristow, told BBC Radio 4′s Today programme that the effect of turning to nukes would be too detrimental to Russia’s international reputation. He said: “Russia has no more interest in getting into direct conflict with Nato than Nato does with Russia.”
Then again, as retired US army colonel Daniel Davis told The Guardian: “There is little [Putin] won’t do when he feels it is necessary to win on the battlefield.”
What nuclear power does Russia have?
Taiwan and Japan are boosting their missile threat too, according to the Bulletin of the Atomic Scientists.
This organisation has also estimated that Russia only has 4,447 warheads; 1,588 on ballistic missiles and at heavy bomber bases, and almost 3,000 more warheads being held in reserve.
But Russia is incredibly secretive about this supply, so it’s hard to know for sure.
The main concern is that Russia is thought to have intercontinental ballistic missiles though which could stretch to London, or even Washington – one can reach the UK from Russia in just 20 minutes.
These missiles would have a yield of between 300 and 800 kilotonnes of the TNT equivalent – enough to destroy the capital cities of the US, UK or France.
Russia could also set off limited nuclear explosions, just to subdue its opponents – these are called tactical nuclear weapons.
Putin, his defence minister or chief of general staff have to authorise the detonation.
What has happened when we used nuclear in the past?
Nuclear weapons do cause devastation on the few occasions they’ve been used.
There are only two instance of nuclear weapons being employed in history – in Hiroshima and Nagasaki, in 1945. Both were detonated by the US in a bid to end World War 2 by weakening Japan. Together, it’s estimated up to 226,000 people died.
In March, at the start of the war, both of these cities wrote to Putin calling for nuclear weapons not to be detonated.
It’s worth remembering the Chernobyl disaster of 1986, in Ukraine, followed an accident at the local nuclear power plant. The true death count is hard to understand because many people died due to the long-term effects of radiation, but the confirmed death toll is less than 100.
There was also the Fukushima nuclear disaster in Japan in 2011 too, after an earthquake caused disruption at another power plant. Only one person has been attributed to the accident, but thousands may have died indirectly from the event.
Both of these events received the maximum classification (level 7) on the International Nuclear Event Scale.
Now, Zaporizhzhia’s nuclear plant has been a significant concern throughout the war. As Ukraine’s largest power plant, it is close to the front line of fighting and has been controlled by Russian soldiers while still being run by Ukrainian technicians. There are fears that a nuclear accident could stem from this, too, if it was shelled.