Russia's Federal Security Service (FSB) has accused Crimean Tatar activists of orchestrating and carrying out attacks with Kyiv's support, allegations described as "fantasy" by the Ukrainian Security Service.

The FSB said in a May 21 statement that an alleged group of plotters was led by Erol Veliyev, a parliamentary assistant to Ukrainian lawmaker Mustafa Dzhemilev, a veteran Crimean Tatar leader, as reported by Radio Liberty.

Rights groups and Western governments have denounced what they call a campaign of repression targeting members of the Turkic-speaking Crimean Tatar minority and others who opposed Moscow's seizure of the Black Sea peninsula in March 2014.

The majority of Crimean Tatars opposed the Russian takeover of their historic homeland.

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The FSB accused Crimean Tatar activists of establishing, participating in, and recruiting for an extremist group – charges that can be punished by up to 10 years in prison.

It said the group led by Veliyev acted on orders from Refat Chubarov – chairman of the Mejlis, the Crimean Tatars' self-governing body that Russia has outlawed – "with support" from the SBU.

In Kyiv, a spokeswoman for the SBU told RFE/RL that she would not comment on the FSB's "latest fantasy."

The statement said that in January the group set the home of Crimea's Moscow-backed chief mufti, Emirali Ablayev, on fire.

In April, Russia said it had detained one of the alleged members, Oleksandr Steshenko, as he entered Crimea to prepare "provocations."

Ukraine's Foreign Ministry at the time asked Moscow for explanations and demanded that his whereabouts be revealed.

Russian television has shown FSB footage of an unnamed man, apparently Steshenko, giving details to investigators.

Two other Crimean Tatars, including Dzhemilev's assistant, Veliyev, have been declared wanted by Russia.

Russia formally banned Dzhemilev from entering Crimea for five years immediately after annexing the peninsula.