Human rights watchdog Amnesty International slammed the trial against Chiygoz as a "sham" on Monday.

The case "epitomizes the ongoing persecution of these activists whose only 'crime' is to vocally oppose Crimea's annexation by Russia," said Oksana Pokalchuk, the head of Amnesty's Ukrainian branch.

Previously, Crimea's top court sentenced Chiygoz to eight years of hard labor over a rally he helped organize in February 2014. The rally was held to protest the upcoming Russian annexation of the peninsula. At the time, Chiygoz served as deputy chief of Mejlis of the Crimean Tatar People, which is a traditional decision-making assembly for the mostly Muslim minority.

Read more: 'Living atop a powder keg' - Crimea Tatars fear Russia

Thousands of Tatars showed up for the 2014 protest in front of the Crimea parliament. The event soon turned violent, with two people killed and 79 injured in the scuffle. Just days later, masked Russian troops took over key state buildings in Crimea and hoisted Russian flags above them. Moscow soon organized a referendum and declared annexation some three weeks later.

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First Moscow, then Strasbourg

Russian authorities arrested Chiygoz, who remained a vocal critic of the takeover, in early 2015. Moscow also banned the Tatars' Mejlis in 2016 as an extremist organization, dismantling and jailing many of its activists.

Read more: Crimean Tatar leader criticizes German politicians in a DW interview

Chiygoz's lawyers are preparing to appeal to Russia's Supreme Court, the Ukraine-based head of the Mejlis, Refat Chubarov, said on Monday.

"One can already forecast its decision - it will support the decision by Crimea's illegal supreme court. Accordingly, our next step will be the European Court of Human Rights," he added.

dj/jm (AP, AFP, Reuters, Interfax, Ukrainski Novini)