Russian authorities in annexed Crimea on Monday were holding trials for 86 Crimean Tatars who had staged solo protests against Moscows rule in October, a local leader and rights groups said.

Amnesty International in a statement called it a "brazen crackdown", insisting the protests were "entirely legal."

The Crimean Tatars are a Turkic-speaking Muslim people native to Crimea who were deported under Soviet dictator Joseph Stalin and only returned to their homeland in the 1990s under Ukrainian rule.

They largely opposed Moscow's 2014 annexation of the Black Sea peninsula, which prompted the new Russian authorities to ban their governing body and close independent media.

Crimean Tatar community leader Nariman Dzhelyal told AFP that 86 members of the Muslim ethnic group went on trial in Crimea on Monday for holding individual political protests on October 14.

Rights lawyer Emil Kurtbedinov confirmed the figure, saying "the authorities have lumped together as one group people who came out on solo protests in various corners of Crimea and in the majority of cases don't even know each other."

Dzhelyal, the first deputy leader of the Crimean Tatars' banned Mejlis assembly, told AFP: "This is just a kind of conveyor belt with the aim of punishing people who weren't afraid to speak out."

He said that so far 10 trials have been completed, with activists fined up to 15,000 rubles ($256).

Dzhelyal accused the courts of issuing pre-determined verdicts. At one trial he witnessed the judge read out the wrong name while pronouncing the sentence.

Trials were ongoing in five cities and towns including the regional capital Simferopol and a number of villages, said Crimean Solidarity activist group.

On October 14, Crimean Tatars held individual protests around the peninsula, often on roadsides, holding placards with slogans such as "Crimean Tatars aren't terrorists", "Stop abusing our people" and "Freedom for political prisoners."

The protests came after the latest wave of detentions and house searches targeting Crimean Tatars.

In Russia, it is legal for a single person to hold a "solo picket" or lone demonstration, without notifying the authorities.

But in this case, activists were accused of taking part in a protest that was jointly organised, and therefore "abusing their right" to solo protests, Dzhelyal said.

Ukraine's foreign ministry spokeswoman Mariana Betsa on Twitter said Kiev "categorically condemned the kangaroo courts in occupied Crimea."

She said that Russia aimed to "break, suppress and destroy the native population."