NATO secretary-general Jens Stoltenberg has warned of “severe consequences for Russia” if Vladimir Putin were to use nuclear weapons in Ukraine, amid escalating rhetoric from Moscow and its allies.

“The nuclear rhetoric is dangerous. It’s reckless”, - Stoltenberg told NBC’s Meet The Press.

Any use of nuclear weapons would “change the nature” of the Ukraine conflict”, he added.

“A nuclear war cannot be won and must never be fought. And this is a message that NATO and NATO allies convey clearly to Russia”, - Stoltenberg said.

His remarks follow some of Vladimir Putin’s sharpest rhetoric to date on Moscow’s willingness to use nuclear force as its military campaign suffers defeats in Ukraine.