Ukraine's navy chief swears allegiance to Crimea's pro-Russian regional authorities, another twist in the unfolding saga.

Denis Berezovsky faces treason charges after he failed to resist and laid down his weapons during the Russian blockade of his headquarters.

Another admiral's taken his place in charge of the navy as prosecutors launched a criminal investigation against him.

On Sunday there were pro- and anti-Russian demonstrations a day after Moscow approved military intervention on Ukraine's soil.

The bloodless seizure of Crimea by Russian forces has unleashed a wave of international condemnation and calls for their withdrawal.

NATO's secretary general says Moscow's actions are illegal.

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

"Military action against Ukraine by forces of the Russian Federation is a breach of international law. It contravenes the principles of the NATO-Russia Council and the partnership fo