KIEV (Reuters) - Crimea's supreme court banned Crimean Tatars' highest ruling body on Tuesday, declaring it an "extremist" organisation in a move one exiled leader said was part of a Kremlin drive to crush the minority ethnic group on the Russia-annexed peninsula.

Most Crimean Tatars, a Muslim people indigenous to the Black Sea region, opposed Russia's seizure of the territory from Ukraine in March 2014. Representatives say they have since faced discrimination and hardship as they come under pressure to align themselves with the Russia-backed authorities.

Regional Prosecutor General Natalia Poklonskaya said the court had banned the Tatars' assembly or Mejlis because its leaders had sought to destabilise Crimea since the takeover.

The Mejlis leadership use "propaganda of aggression and hatred towards Russia, inciting ethnic nationalism and extremism in society," Poklonskaya said in a Facebook post.

The court decision follows the silencing of a Tatar-language TV station in Crimea in April 2015 and recent reports of police intimidation and brutality towards opponents of annexation.

The 1944 Soviet-era deportation of some 200,000 Tatars to Siberia and Central Asia killed many thousands and is a reason for Tatars' deep mistrust of Russian authorities. Though the Tatars have been allowed to return to Crimea, many still associate Russian rule with exile, oppression and suffering.

Council of Europe Commissioner, Nils Muiznieks, urged the court to reverse the ban.

"Equating (the assembly) with extremism paves the way for stigmatisation and discrimination of a significant part of the Crimean Tatar community and sends a negative message to that community as a whole," he said in a statement.

Since the annexation, while clamping down on Tatars openly loyal to Ukraine, Russia has sought to defuse opposition from the community as a whole with gestures such as granting legal rehabilitation to Tatars for their suffering under Soviet dictator Josef Stalin, and official status to their language.

Crimean Tatar leader Refat Chubarov, who now lives on the Ukrainian mainland, said the court's decision was unjustifiable.

"The occupiers in Crimea are doing everything to crush Crimean Tatars and force everyone to be silent," he told journalists in Kiev.

(Reporting by Alessandra Prentice and Pavel Polityuk; editing by Ralph Boulton)