Crimea's acting head Sergey Aksyonov has been appointed the republic's chief.
Aksyonov Thursday took oath after all 75 members of Crimea's legislative body, the state council, voted in support of his candidacy, Xinhua reported.
He will also serve as the prime minister of Crimea's parliament under the constitution.
Aksyonov's political career started in 2008 by establishing the Russian Unity party.
He was named the prime minister by the Crimean parliament ahead of a referendum on the region's independence March 16.
The Crimean parliament declared independence from Ukraine March 17, after official results showed 96.77 percent of the Crimean voters chose to join Russia in a referendum, which was not recognised by Ukraine and the West.
Russian President Vladimir Putin signed a law on Crimea's accession to Russia a day later, stressing that the referendum was fully in accordance with international law.
