Putin's open assertion of the right to deploy troops in a country of 46 million people on the ramparts of central Europe creates the biggest direct confrontation between Russia and the West since the Cold War.
It followed days of warnings from U.S. President Barack Obama and other Western leaders that Russia must not intervene, and assurances from Moscow that it would not do so.
Putin swiftly secured unanimous approval from Russia's senate for the use of armed force on the territory of his neighbour, citing the need to protect Russian citizens, the same reason he gave for invading tiny Georgia in 2008.
Britain summoned the Russian ambassador. EU ministers were due to hold emergency talks. Czech President Milos Zeman recalled the Soviet invasion of Czechoslovakia in 1968.
Troops widely believed to belong to Moscow have already seized Crimea, an isolated peninsula in the Black Sea where Moscow has a large military presence in the headquarters of its Black Sea Fleet. The campaign there has been bloodless so far, with Kiev's new authorities powerless to intervene.
Scores were also hurt on Saturday in clashes between pro-Russian demonstrators and supporters of Kiev's new authorities in eastern cities - areas near the Russian frontier, where Moscow is staging war games on high alert.
Putin asked parliament to approve force "in connection with the extraordinary situation in Ukraine, the threat to the lives of citizens of the Russian Federation, our compatriots" and to protect the Black Sea Fleet in Crimea. The authorisation to use force in Ukraine would last "until the normalisation of the socio-political situation in that country".
http://uk.reuters.com/article/2014/03/01/uk-ukraine-idUKBREA1H0EM20140301
