A US expert has warned Russia's threat of using nuclear weapons in Ukraine creates the risk of other powers becoming involved in the conflict.
Russian President Vladimir Putin made the nuclear threats this week, which have been slammed by world leaders as dangerous and reckless.
Putin also announced 300,000 military reservists would be sent to Ukraine in what he called a "partial mobilisation", sparking many demonstrators to take to the streets in Russian cities - hundreds of whom were arrested.
Giving his assessment of Putin's latest rhetoric, nuclear nonproliferation expert George Moore said it was "disturbing".
"He's been doing disturbing things with making subtle - and maybe not so subtle - nuclear threats - since he began the invasion or 'special operation,'" said Dr Moore, a former senior analyst at the International Atomic Agency's nuclear security office.
"Hopefully, it's not as disturbing as some people have given it credit for," he told AM.
Putin's threat outraged world leaders, many of whom were currently gathered at the UN General Assembly in New York.
Putin using nuclear weapons would cause physical carnage as well as "political destruction", Dr Moore said.
"He could destroy several villages or even a major metropolitan area," he said. "Just like Hiroshima and Nagasaki, the world didn't stop because of those but, in those days, we were in a major world war - now we're looking at a situation where this could… if he were to use nuclear weapons, rapidly escalate and get out of control."
The US has said Putin was shredding international order "before our eyes" with his threats.
Dr Moore said Putin was "walking a very, very dangerous line" with his comments.
"One of the real dangers of what he's doing is if he changes his readiness state, for example, for strategic nuclear weapons, other countries… might feel compelled to follow."
That would create a dangerous situation, Dr Moore said.
"The higher the readiness states go, the more chance there is of something being done inadvertently, accidentally."
