Moscow is celebrating. Russian President Vladimir Putin says Crimea is returning home. He was speaking to the crowd in Red Square after signing a treaty with Crimean authorities, making Ukraine's autonomous region part of Russia again.

Russia's President Vladimir Putin addresses the Federation Council in Moscow's Kremlin on Tuesday, March 18, 2014.

"Today is a very joyful and festive day. Dear Russian citizens, dear Crimeans, Sevastopol residents, after a hard, long, tiring trip, Crimea and Sevastopol are returning to their home port, to their native shore, to Russia." Putin said.

More than 100,000 people came out to celebrate the historical event. The treaty was signed in the the Saint George Hall at the Kremlin. The next step is endorsement by Russia's Constitutional Court, then ratification by both houses of parliament. The procedure could be completed by the end of the week.

Putin has dismissed western criticism of Sunday's referendum - in which Crimean residents overwhelmingly backed leaving Ukraine and joining Russia. He said the vote was in line with international law, and reflected the right for self-determination. Putin has vowed to retaliate over sanctions imposed by the West on Russia and he says Russia does not want to seize more of Ukraine.