MOSCOW (AP) — Two prominent Crimean Tatar leaders who were imprisoned in Russian-occupied Crimea have been released and flown to Turkey, Ukraine's president said Wednesday.

President Petro Poroshenko in a tweet Wednesday thanked the Turkish president for his help in mediating the releases of Ilmi Umerov and Akhtem Chiygoz.

Chiygoz, the deputy chairman of the Mejlis representative body for the Tatars in Crimea, had been sentenced to eight years in prison on a charge of organizing a riot during Russia's 2014 annexation of the peninsula. Russia sent troops to Crimea and declared the annexation about three weeks later.

Umerov, another deputy chairman of the Mejlis, had been sentenced to two years in prison for his criticism of Russia's annexation.

Crimea's Supreme Court effectively banned the Mejlis in April, declaring it an extremist organization.

Crimean Tatars, an ethnic group of Turkic origin, suffered a mass deportation at the hands of Soviet authorities in 1944. In 2014, they opposed Russia's annexation of the Ukrainian peninsula. Chiygoz's and Umerov's incarceration followed months of persecution, expulsions and jailings of Tatar leaders as well as rank-and-file protesters.

Nikolai Polozov, who represented both Chiygoz and Umerov in court, confirmed to the Tass news agency that the two Tatar leaders had been released but would not say if they have been pardoned. He was not immediately available for comment.

Tatars, including prominent leaders with Soviet dissident backgrounds like Mustafa Dzhemilev, were initially invited to contribute to the new government in Crimea. But a swift ban on Tatar assemblies and Russian government's demands in Crimea put a strain on efforts to work together.

Dzhemilev and Mejlis Chairman Refat Chubarov live in Kiev, the Ukrainian capital, where they were elected to the Ukrainian parliament after Russian authorities barred them from entering Crimea.