Art teacher Daniil Klyuka believes the headmistress of the provincial Russian school where he worked reported him for doodling horns on pictures of officials in a newspaper.

The 28-year-old was later sentenced to 20 years in jail.

His case illustrates the severity of the crackdown on dissent -- both real and imagined -- in Russia since the invasion of Ukraine.

And how ordinary Russians are again living under the shadow of denunciation, the old Soviet practice of informing on colleagues, neighbours, friends and even family.

Until last winter, Klyuka lived a quiet life in Dankov, a town 300 kilometres (190 miles) south of Moscow, whose chief claim to fame is that the renowned novelist Leo Tolstoy died at a railway station nearby.

On the website of the state school where he worked, there are still photos of the classroom where he taught, decorated with posters of famous paintings, including a self-portrait by Van Gogh.

But Klyuka's life took a nightmarish turn one day in February 2023 when he was arrested by masked members of Russia's feared FSB security service.

He was accused of sending 135,000 rubles (around $1,380) in cryptocurrency to Ukraine's ultranationalist Azov brigade, classified as "terrorist" in Russia -- a charge he denies.

Klyuka believes all this happened because he idly scribbled moustaches, horns and beards onto photos of officials in a pro-Kremlin newspaper that staff at his school were expected to read.

AFP has been able to piece together his descent into the depths of the Russian penal system, where prisoners can sometimes disappear without a trace, through letters he has exchanged with a Russian anti-war activist exiled in Italy.

Antonina Polishchuk, 43, gradually learned what had happened to him after responding last year to an appeal to write to Russian political prisoners, some of whom have the right to receive letters.

She decided to write to Klyuka because of a shared love of architecture and anime.

"I'm interested in........

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