The prosecutor in Russian-occupied Crimea has filed a request with that territory's Supreme Court to ban the Crimean Tatars' self-governing body, the Mejlis.
The Mejlis has refused to recognize Russia's forced annexation of the peninsula from Ukraine nearly two years ago and played a key role in the consolidation of efforts on behalf of Crimean Tatars.
Natalya Poklonskaya signed the request on February 15 to brand the Mejlis "an extremist organization," Russian news agencies reported.
The reports say Poklonskaya handed a copy of the legal challenge to a leader of the Mejlis, Nariman Celal, the same day.
Many Crimean Tatars fled Crimea during or after its military seizure by Russia in early 2014, and others who remained have complained of harassment or even disappearances under the Moscow-backed authorities on the peninsula.
The European Parliament this month overwhelmingly approved a resolution to condemn Russia for its treatment of the minority group, which one member said, "have been persecuted from the very beginning of the Russian invasion."
Poklonskaya's move comes four days after the Russian authorities who control Crimea arrested several Crimean Tatars on suspicion of belonging to Hizb ut-Tahrir, an Islamist political organization that is banned across Central Asia and Russia.
Crimean Tatars activists rejected the charges, saying that they were politically motivated.
Established in 1991 and legalized by the Ukrainian government in 1999, the Mejlis has been known as an organ that addressed issues related to Crimean Tatars to Kyiv and international bodies.
The Mejlis was led for many years by the veteran leader of the Crimean Tatars, Soviet-era dissident Mustafa Dzhemilev.
Since November 2013, the Mejlis has been led by Refat Chubarov.
Dzhemilev and Chubarov, both Ukrainian lawmakers, have been barred from entering Crimea for five years by Crimea's pro-Moscow leadership.
The Organization for Security and Cooperation In Europe's (OSCE) Office for Democratic Institutions and Human Rights and the OSCE High Commissioner on National Minorities issued a report in September saying that since Russia's land grab, fundamental freedoms had "deteriorated radically" for many in Crimea, especially for pro-Ukrainian activists, journalists, and the Crimean Tatar community.
Crimean Tatars have been reported abducted, and in some cases later found dead, while others have been arrested and charged with extremism since the annexation.
Crimean Tatars are native to the Black Sea peninsula but were deported to Central Asia by Soviet dictator Josef Stalin in 1944. They began returning in large numbers to Crimea in the late 1980s and now compose more than 12.5 percent of Crimea's population of 2.5 million.
With reporting by TASS and Interfax