Russia's put 150, 000 of its troops on high alert for war games near the border with Ukraine.

It's the Kremlin's boldest gesture yet after days of sabre rattling since Ukraine's President Viktor Yanukovich was toppled.

Moscow's denying the previously unannounced drill was linked to events in Ukraine.

Even so, it's come in the face of increasingly strident statements about the fate of Russian citizens and interests.

NATO defence ministers meeting in Brussels issued a statement supporting Ukrainian sovereignty and independence.

NATO's secretary general said he had been notified of the Russian military drill.

(SOUNDBITE)(English) NATO SECRETARY GENERAL ANDERS FOGH RASMUSSEN SAYING:

"I'm not in a position to go into details about the scope or the purpose of this exercise. All I know is that this military exercise has been notified, informed. I suppose the Russians have lived up to all their obligations as regards transparency but as I've been in