President Vladimir Putin has signed a treaty to incorporate Crimea into Russia.
It comes after Sunday’s referendum in Crimea, which saw overwhelming support for a union with Russia.
Putin signed the law after a speech to Russia’s parliament, in which he hit back at his critics.
He condemned Ukraine’s “so-called” authorities, saying they had stolen power in a coup and had opened the way for “extremists” who would stop at nothing to determine the future of the country.
Addressing a joint session of Russia’s parliament, Putin said: “Those who were behind recent events, they were … preparing a coup d’etat, another one. They were planning to seize power, stopping at nothing. Terror, murder, pogroms were used.”
He called them “nationalists, neo-Nazis, Russophobes and anti-Semites” adding: “It is primarily they who are deciding how Ukraine lives today. The so-called Ukrainian authorities introduced a scandalous law on the revision of the language policy, which directly violated the rights of the national minorities.”
He said Moscow sees Western attempts to frighten Russia with sanctions as aggression and will retaliate.
Earlier Putin signed a decree which recognises Crimea as a sovereign and independent state. The Kremlin said the order would take immediate effect.
It follows the Crimean parliament’s earlier decision to declare independence from Ukraine after the region’s referendum on Sunday. That saw a massive 97 percent of voters back a break-away from Kyiv.
‘Rule of the gun’
The European Union, United States and Ukraine have all condemned the ballot as illegal.
In his speech to Russia’s parliament Putin said US foreign policy is dictated not by international law, but by the “right of the strong”.
“Our Western partners headed by the United States prefer not to be guided by international law in their practical policies, but by the rule of the gun,” he said.
“They have come to believe in their exceptionalism and their sense of being the chosen ones. That they can decide the destinies of the world, that it is only them who can be right.”
In addition to commandeering all Ukrainian state property, Crimea’s leaders have declared Ukrainian law invalid.
They also announced they will adopt the Russian rouble, and the clocks will move two hours forward to Moscow time at the end of March.