Russia and Crimea Tuesday signed a treaty to make the latter territory part of Russia, the Associated Press reported.
The move came after President Vladimir Putin said on Tuesday that Russia would never seek a confrontation with the West, but that it will defend its own interests.
"We must decide for ourselves whether we are ready to stand up for our national interests, or just carry on giving them away forever?" he asked a joint session of parliament.
To thunderous applause, and some tears in the audience, Putin defended Russia's actions in the crisis over the Black Sea peninsula, which has created one of the worst crises between Russia and the West since the end of the Cold War.
"Some Western politicians scare us not only with sanctions but also with the prospect of worsening internal problems," he said, adding that Russia would never want to start a confrontation with the West.
"We consider such statements irresponsible and obviously aggressive and will respond appropriately to this."
"The [Crimean] issue has a vital importance, a historic importance for all of us," Putin said in an address at the Kremlin.
"In the hearts and minds of people, Crimea has always been and remains an inseparable part of Russia. This commitment, based on truth and justice, was firm, was passed from generation to generation," he said in a speech that lasted 47 minutes.