Armed men took control of two airports in the Crimea region on Friday in what the new Ukrainian leadership described as an invasion by Moscow's forces, and ousted President Viktor Yanukovich surfaced in Russia after a week on the run.

Yanukovich said Russia should use all means at its disposal to stop the chaos in Ukraine as tension rose on the Black Sea peninsula of Crimea, the only region with an ethnic Russian majority and the last major bastion of resistance to the overthrow of the Moscow-backed leader.

Kiev's border guard service said more than 10 Russian military helicopters had flown over the peninsula and Russian servicemen had blockaded one of its units in the port city of Sevastopol.

A serviceman at the scene confirmed that he was from Russia's Black Sea Fleet, part of which is based in Sevastopol, and said they were there to stop the kind of protests that ousted Yanukovich in Kiev.

The fleet denied its forces were involved in seizing the military airport near Sevastopol, where armed men later also occupied the runway, Interfax news agency said, while a supporter described the armed group at the civilian international airport in Simferopol as Crimean militiamen.

Ukraine's commercial airline said later that it had been refused entry into Crimean airspace.

Moscow has promised to defend the interests of its citizens in Ukraine and has said it will not intervene by force. But its rhetoric since the removal of Yanukovich a week ago has echoed the run-up to its invasion of Georgia in 2008.

The U.N. Security Council called an emergency session for later on Friday at the request of Ukraine's new leaders, who warned the country's territorial intergrity was threatened.