Putin orders Russia's nuclear deterrence forces on high alert

Russian president Vladimir Putin has ordered his military to put the country's nuclear deterrence forces on high alert in response to "aggressive statements" by NATO countries.

The order, which was announced by the TASS news agency, came at a meeting between Putin, defence minister Sergei Shoigu and chief of the General Staff of the Armed Forces of Russia Valery Gerasimov.

"Senior officials of the leading NATO countries also allow aggressive statements against our country, therefore I order the Minister of Defense and the Chief of the General Staff [of the Russian Armed Forces] to transfer the deterrence forces of the Russian army to a special mode of combat duty," Putin said in the statement, which was quoted by state-run TASS.

It is not immediately clear what the "special mode of combat duty" entailed. Putin has warned foreign countries not to interfere in his ongoing invasion of Ukraine, saying it could lead to "consequences they have never seen." He has positioned anti-air missiles and other advanced missile systems in Belarus and deployed his fleet to the Black Sea in an effort to prevent a western intervention in Ukraine.

The Russian invasion has left hundreds dead. Russia has launched missile strikes against buildings in Kyiv, Kharkiv and other major Ukrainian cities as it threatens an all-out assault not seen since the time of the second world war.