Russian President Vladimir Putin on Saturday asked the upper house of parliament to approve the use of Russian troops in Ukraine, the Kremlin said, despite warnings from the US not to intervene.
The parliament unanimously approved Putin's request.
"In connection with the extraordinary situation in Ukraine and the threat to the lives of Russian citizens... I submit to the Federation Council a request to use the armed forces of the Russian Federation on Ukrainian territory until the normalisation of the political situation in that country," the Kremlin quoted Putin as saying in the document.
Putin said that Russia also had to protect servicemen from its Black Sea Fleet which is based on the Ukrainian Black Sea peninsula of Crimea "fully in line with an international accord".
The request was made on the basis of point "G" of the first part of section 102 of the Russian constitution on allowing the use of Russian troops beyond the borders of the country.
There were no further details on the document and Putin has yet to speak publicly about the situation in Ukraine since the overthrow of president Viktor Yanukovych last week.
Putin's move came after the heads of both the lower and upper houses of parliament on Saturday urged him to take measures over the situation in Ukraine and in particular the overwhelmingly pro-Russian peninsula of Crimea.
Federation Council speaker Valentina Matviyenko said earlier that it is possible "to send a limited contingent of troops to ensure the security of the Black Sea Fleet and Russian citizens."
Meanwhile, the speaker of the State Duma lower house Sergei Naryshkin read out a request in the name of all MPs for Putin to use "all possibilities" to restore stability in Crimea.
Ukraine's new Defence Minister Igor Tenyukh said Saturday the Russian forces are already in the country, accusing Russia of sending 30 armoured personnel carriers and 6,000 additional troops into Crimea.
Unlike most legislation in Russia, the use of armed forces abroad only requires the approval of the rubber-stamp Federation Council without any need for a preliminary okay from the State Duma lower house.
The Kremlin has been rattled by the sudden overthrow of Yanukovych and the installation of pro-EU and sometimes staunchly anti-Russian new authorities in his place, fearing a permanent loss of influence in Russia's ex-Soviet neighbour.