President Vladimir Putin formalized his country’s annexation of Ukraine’s Crimea on Tuesday when he signed a treaty that returned the peninsula to Russia.

A day earlier, lawmakers in the Moldovan breakaway region of Transnistria requested similar admission into the Russian Federation.

Putin announced the annexation in an address to a joint session of parliament in Moscow’s Kremlin, days after an overwhelming majority of the Crimea’s population had voted in favor of joining Russia.

Denounced by Ukraine’s government and Western nations as illegitimate, the referendum saw almost 97 percent of Crimeans voting to become Russian with turnout at 83 percent.

The majority of the peninsula’s residents are ethnic Russians but 12 percent are Tatars, the native population that was deported en masse to Central Asia by Soviet leader Joseph Stalin in 1944 on suspicion of collaborating with the Nazis. They have been returning since the Soviet regime collapsed in 1991 and many boycotted the plebiscite that gave them no choice of remaining part of Ukraine with a high degree of autonomy.

The city of Sevastopol, which headquarters Russia’s Black Sea Fleet, is likely to be admitted into the Russian Federation as a separate entity with a status similar to Moscow and Saint Petersburg. Russian lawmakers are expected to ratify the treaty later this week.

Russian troops entered the Crimea in late February after Ukraine’s elected president, Viktor Yanukovich, was deposed following months of protests against his decision to pull out of an associated agreement with the European Union in favor of deeper ties with his country’s former Soviet master, Russia. Putin has denied sending troops but vowed to protect Russian speakers and Russian interests in a region that was part of the Russian Empire for almost two centuries before Soviet leaders transferred it to Ukraine in 1954, then a Soviet satellite state.

Russia’s annexation of the Crimea appeared to have rekindled separatist sentiments in another former Soviet republic, Moldova. Some 200,000 of its citizens living in the eastern region of Transnistria broke away from the country in 1990. While Russia has not formally recognized its independence, it has some 2,000 troops stationed there and many Transnistrians also hold Russian citizenship.

In 2006, 97 percent of Transnistrians voted to join Russia in a referendum.

Moldova, which did sign an association agreement with the European Union late last year, warned Russia on Tuesday that annexing Transnistria would be a “mistake.”