From the Wikipedia page 
The Karelian Autonomous Soviet Socialist Republic (Russian: Каре́льская Автоно́мная Сове́тская Социалисти́ческая Респу́блика, tr. Karelskaya Avtonomnaya Sovetskaya Sotsialisticheskaya Respublika; Finnish: Karjalan autonominen sosialistinen neuvostotasavalta), or, in short, the Karelian ASSR (Russian: Каре́льская АССР, tr. Karelskaya ASSR; Finnish: Karjalan ASNT), sometimes referred to as Soviet Karelia or simply Karelia was an autonomous republic of the Russian SFSR, Soviet Union, with the capital in Petrozavodsk.
The Karelian ASSR was formed as a part of the Russian SFSR by the Resolution of the Presidium of the All-Russian Central Executive Committee (VTsIK) of June 27, 1923 and by the Decree of the VTsIK and the Council of People's Commissars of July 25, 1923 from the Karelian Labor Commune. In 1927, the ASSR was divided into districts, which replaced the old volosts.