Putin puts Russia's nuclear deterrent forces on alert

Russian President Vladimir Putin has put Russian nuclear deterrent forces on high alert amid tensions with the West over Ukraine.

Putin told state TV that NATO powers have made "aggressive statements" along with the West imposing hard-hitting financial sanctions against Russia, including the president himself.

He ordered the Russian defence minister and the chief of the military's General Staff to put the nuclear deterrent forces in a "special regime of combat duty".

The US Ambassador to the United Nations says Putin's order shows the Russian leader is "escalating conflict in a manner that is unacceptable".