MOSCOW — With the new government in Kyiv weak and in disarray, Russia has made an aggressive move into Crimea. In a unanimous vote, Russia’s upper house of parliament Saturday gave President Vladimir Putin the green light to send troops to Ukraine, without specifying where.

Ukrainian Prime Minister Arseniy Yatsenyuk is warning Russia that military intervention would mean war between the two neighbors; acting Ukrainian President Oleksandr Turchynov said Saturday he has put the country’s armed forces on combat alert following Saturday’s vote in Russia, during which legislators also asked Putin to withdraw Russia’s ambassador to Washington.

Russian legislators said they were insulted by U.S. President Barack Obama’s statement on Ukraine Friday. Obama said the U.S. is “deeply concerned by reports of military movements taken by the Russian Federation inside of Ukraine.

He went on to say there would be “costs for any military intervention in Ukraine.”

The White House says Obama held a long telephone conversation with Putin Saturday, expressing deep concern for what it calls the clear violation of Ukrainian sovereignty and international law.

The president said the United States is suspending participation in meetings to prepare for the G8 economic summit later this year in Sochi, Russia.

Russian news agencies say Putin told the president that Russia reserves the right to protect Russian speakers if there is violence in Crimea or eastern Ukraine.

On Saturday, Ukraine’s deposed president, Viktor Yanukovych, and Sergei Aksenov, Crimea’s new prime minister, appealed for Russian troops to enter Ukraine’s Autonomous Republic of Crimea.

Aksenov’s Russia Unity Party won only three parliament seats in regional elections in 2010, and won no seats in Ukraine’s 2012 national elections.

Story continues after video: Elizabeth Arrott’s on the ground in Simferopol.

But on Thursday, armed Russian-speaking men invaded Crimea’s parliament. At gunpoint, a slim majority elected Aksenov.

UN calls for ‘cool heads’

Ukrainian Ambassador to the United Nations, Yuriy Sergeyev, told the Security Council Saturday that 15,000 Russian troops are already in Crimea under the pretense of protecting Russian citizens, and that his country is calling on the U.N. to do everything possible to stop what he calls aggression against Ukraine.

Russian Ambassador Vitaly Churkin blamed the West for ratcheting up tensions in Ukraine and backing protests that ousted President Viktor Yanukovych.

The United Nations says now is the time for “cool heads to prevail.”

In Moscow, political analyst Pavel Felgenhauer says Moscow is following a political strategy that worked well in the Soviet era.

“This is from the Russian textbook — there is nothing new at all,” he said, referring to Soviet-era invasions. “It happened in Afghanistan. It happened in Hungary.”

In those cases, Soviet troops invaded countries after appeals by leaders installed by the Kremlin.

In Crimea, Moscow acted before the nicety of an appeal by the region’s new prime minister — and during a period with high political tension, but little violence.

Starting Friday, Russian army troops took over Crimea’s three airports, and military helicopters and transport planes shuttled troops and supplies into the peninsula. Russian soldiers and Navy ships blockaded Ukrainian military bases. Armed checkpoints manned by Russian-speaking men now control the sole highway from the mainland to the peninsula. Russian consular officials started distributing Russian passports to policemen in Crimea.

In Kyiv, Ukrainian government officials say that 6,000 Russian soldiers were in Crimea by Saturday.

“Russia has started blatant aggression against Ukraine under the guise of military exercises,” said Ukraine’s interim President Oleksandr Turchynov. “The Russian Federation has sent troops to Crimea, which have not only seized the Crimean parliament and the Council of Ministers but are also trying to take control of communication facilities and the bases where the servicemen are stationed.”

Only two months ago, Russian state television praised Ukrainians as their Slavic brothers. In a total switch, state television now describes Ukraine as a country controlled by “fascist nationalists.” Television screens show videos of Russian army tanks churning through mud, part of a 150,000-man military exercise across the border from eastern Ukraine.

Dmitri Trenin, director of the Carnegie Moscow Center says the military exercise is designed to tell Kyiv and the West to back off from Russian-speaking areas of Ukraine.

“The timing of this is clearly sending a message to the people in Kyiv — don’t go too far, don’t try to establish ‘constitutional order’ in Crimea, don’t intervene by force in Eastern Ukraine,” he said in a conference call. “It’s also, I think, a message to Washington and NATO in the sense that Russia is prepared to defend its interests in this part of the world.”

Emboldened by Russia’s show of force, armed men on Saturday seized government buildings in Eastern Ukraine’s two largest cities — Kharkiv and Donetsk. Soon, Russian flags flapped from the rooftops.

WATCH: Pro-Russian demonstrators storm the Kharkiv administration (courtesy: rferl.org).

Some regional analysts warn that Russia may be biting off more than it can chew.

“Right now our peacekeeping units are going to be tied down in Crimea, and we don’t have that many peacekeeping units,” said Felgenhauer who specializes in military analysis.

And it is unclear how deep the support is in Crimea for annexation by Russia. The prime minister says he will hold a referendum on Crimea’s status on March 30.

The majority of Crimea’s 2 million people are native Russian speakers. But Kyiv has ruled Crimea for nearly 70 years. A large portion of inhabitants identify themselves as Russian speaking Ukrainians.

In addition, Muslim Tatars make up 15 percent of Crimea’s population. During the first half of the 20th century Kremlin policies killed about half the population — through famine in the 1920s and 1930s and mass deportation in 1944. As a result, Crimean Tatars strongly oppose rule by Moscow.

If Russia’s occupation turns violent, Turkey could step in to defend the Tatars. The simplest way would to be close the Bosphorus strait, the exit route for about one third of Russia’s oil exports.

Felgenhauer said of the Turkish government: “They could get rather nasty with Russia. They could put serious pressure on the Russian government.”

Ukraine’s central government has its own levers.

It could cut off a water pipe from the continent that is a primary source of drinking water to Crimea’s arid north. Tourism, the economic mainstay for much of Crimea’s population, could plummet if political tensions remain high over sovereignty.

And Russia can expect sanctions from the West, its major trading partner.

For starters, Western leaders would probably boycott the June summit of G -8 countries. President Putin is planning to host the summit in Sochi, the location of the 2014 Winter Olympic Games — which ended just a week ago. It’s only 400 kilometers across the Black Sea from Crimea.

Yanukovych speech

Ukraine’s fugitive president Viktor Yanukovych speaks at a news conference in Rostov-on-Don, a city in southern Russia, Feb. 28, 2014.

Ousted Urkrainian president Yanukovych resurfaced in the southern Russian city of Rostov-on-Don where he held a news conference Friday, calling on his opponents to stop what he called the “horrible lawlessness” in Ukraine.

Ukrainians have mixed reactions to this first public appearance of Yanukovych who fled Kyiv last week.

While Kyiv and western Ukraine have risen up against Yanukovych, he remains popular in the Russian-speaking eastern and southern regions where economic and cultural ties with Russia remain strong.

His remarks were broadcast around the country on giant television screens.

Galina Shurko, resident of the western Ukraine city of Lviv, is not a supporter of the ousted leader.

“You know, we are really surprised that he’s still saying something,” said Shurko. “We don’t even like to listen to him because of all this pain in our hearts and everything that he has done to Ukraine.”

Meanwhile, Karina, a resident of the northeastern city of Kharkiv said Yanukovych’s re-surfacing in Russia was the logical thing to do.

“Sorry, but what is Viktor Yanukovych to do when some strange people came to power and simply act as some junkies? What should he do? Where should he go? He could have been killed, as simple as that, of course he went to Rostov-on-Don,” she said.

Lena Kleshevnykova, another resident of Kharkiv — Ukraine’s second largest city — is a staunch supporter of the Yanukovych.

“I still consider him our president because the new government came to power in an unlawful way, with military aggression,” said Kleshevnykova.

Some information for this report also provided by Elizabeth Arrott reporting from Simferopol, and Reuters.

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