Crimea's parliament voted to join Russia on Thursday and its Moscow-backed government set a referendum within 10 days on the decision in a dramatic escalation of the crisis over the Ukrainian Black Sea peninsula.
The sudden acceleration of moves to formally bring Crimea, which has an ethnic Russian majority and has effectively been seized by Russian forces, under Moscow's rule came as European Union leaders gathered for an emergency summit to seek ways to pressure Russia to back down and accept mediation.
The Crimean parliament voted unanimously "to enter into the Russian Federation with the rights of a subject of the Russian Federation." Its vice premier said a referendum on the status would take place on March 16.
The announcements, which diplomats said could not have been made without Russian President Vladimir Putin's approval, raised the stakes in the most serious east-west confrontation since the end of the Cold War.
E.U. leaders had been set to warn but not sanction Russia over its military intervention in Ukraine after Moscow rebuffed Western diplomatic efforts to persuade it to pull forces in Crimea back to their bases. It was not immediately clear what impact the Crimean moves would have.