Russian and Ukrainian troops in Crimea are involved in a tense stand-off...Moscow forces have wrested control of Ukraine's Crimea -- a region with an ethnic Russian majority.

At a UN Security Council meeting, Russia says its troops went into the Ukrainian region upon a request by the ousted president, Viktor Yanukovich.

(SOUNDBITE) (English) VITALY CHURKIN, RUSSIAN AMBASSADOR TO THE UNITED NATIONS, SAYING:

"I think it's important to realise that the person who we believe is legally president of Ukraine also shares our concerns of large segments of the Ukrainian population about what is going on and is appealing to Russia to use our armed forces to change the situation and to prevent the situation from further deteriorating."

The Russian UN envoy showed reporters a copy of the letter Yanukovich allegedly wrote to Russian President Vladimir Putin on Saturday.

His statement comes as two Russian warships were spotted passing through Turkey's Bosphorus on the w