KIEV, March 1 -- Ukraine's acting President Alexandr Turchynov said Saturday he has placed the country's armed forces on full combat alert, warning that any military intervention in the country would lead to war.

Speaking alive on Ukrainian TV, he said he had also ordered intensified security at nuclear power plants, airports and other strategic infrastructure.

Russia has no justification for any "act of aggression," Turchynov said in a late night announcement made hours after Russia's parliament gave President Vladimir Putin a green light to use military force to protect Russian interests in Ukraine.

"All explanations about dangers to Russian citizens or Russian- speaking Ukrainians have been devised," he said.

Meanwhile, Prime Minister Arseny Yatsenyuk said he had urged Russia to return its troops to base in the southern Crimea region during a phone call with Prime Minister Dmitry Medvedev and called for talks.

"Military intervention would be the beginning of war and the end of any relations between Ukraine and Russia," Yatsenyuk said.

At a cabinet meeting Saturday, Yatsenyuk called on concerned parties to abandon armed conflict and resolve the crisis through peaceful means.

Yatsenyuk also urged Moscow not to provoke discord in Crimea. " We call on the government and authorities of Russia to recall their forces, and to return them to their stations," he was quoted as saying by the Interfax news agency.

Earlier in the day, Russian Federal Council, or upper house of the parliament, approved Putin's request for using armed forces in Ukraine.

The Kremlin said Putin made the request "in connection with the extraordinary situation in Ukraine, the threat to the lives of citizens of the Russian Federation, our compatriots, and the personnel of the military contingent of the Armed Forces of the Russian Federation deployed in the territory of Ukraine ( Autonomous Republic of Crimea)."

The troops would be used until the "political-social situation in the country is normalized," said the Kremlin.