(Updated March 1, 2014, 7:42 p.m.)
Putin made the request because of what he said was a threat to the lives of Russians and military forces located in naval bases in Crimea.
The Federation Council voted unanimously in support of military action.
The move comes after reports of large Russian troop movements in the southern Ukrainian peninsula of Crimea, and a week after the opposition swept to power in Kiev when ousted President Viktor Yanukovych suddenly left the city.
Russian troops will remain deployed until the “political-social situation in the country is normalized,” the Kremlin said in a statement.
Senators in the Federation Council, which is Russia's upper house of parliament, lined up during an extraordinary session Saturday afternoon to express their support for armed intervention.
Lawmakers accused the United States and European countries of open support for violent protesters in Ukraine.
The decision follows a wave of pro-Russian protests in southern and eastern Ukraine, and calls from the newly elected prime minister of Crimea for Putin to intervene.
The ratcheting up of Russian rhetoric over Ukraine and widespread reports of the presence of Russian troops already maneuvering on Ukrainian soil has provoked outrage in Kiev and condemnation from world leaders.
U.S. President Barack Obama said Friday that he was deeply concerned about Russian troop movements inside Ukraine, and warned that violations of Ukraine’s sovereignty would be deeply destabilizing.
Officials from the interim Ukrainian government have said Russia is trying to provoke conflict, and have called on the Kremlin to withdraw all soldiers back to Russian naval bases on the Black Sea coast.