A Russian Gulag historian acquitted of child porn charges has been detained again for alleged sexual assault and faces 20 years in prison, investigators said Thursday, dealing a huge blow to the country's embattled rights community.
The authorities' turnabout in the high-profile case of Gulag researcher Yury Dmitriyev comes as Moscow hosts the World Cup during what Human Rights Watch has called "the worst human rights crisis in Russia since the Soviet era."
Observers see the treatment of the respected historian and other Kremlin critics as a sign of the country's future direction during the fourth Kremlin term of President Vladimir Putin, who extended his rule until 2024 in a March election.
Dmitriyev was detained as another top dissident, jailed Ukrainian filmmaker Oleg Sentsov, reached day 45 of a hunger strike to demand Moscow release Ukrainian political prisoners.
A spokesman for regional prosecutors, Vitaly Konovalov, said a probe into allegations of sexual assault against Dmitriyev had been launched.
The historian -- who is the head of leading rights group Memorial's branch in Karelia in northwestern Russia -- faces up to 20 years in prison if convicted, Konovalov told AFP.
In a separate statement apparently referring to Dmitriyev's case, investigators alleged an unnamed resident of the northwestern city of Petrozavodsk sexually abused his adopted daughter between 2012 and 2016.
Dmitriyev was detained Wednesday after investigators claimed to have found new evidence, defence lawyer Viktor Anufriyev told AFP.
A court was scheduled to rule on whether to remand Dmitriyev in custody later Thursday.
The 62-year-old's previous case centred on naked photographs of his then pre-teen adopted daughter Natalya seized during a search of his home after an anonymous tip-off to police.
His defence said the photographs were taken to track improvement in the girl's health as she recovered from malnutrition.
Dmitriyev, whose trial sparked an outcry from liberals, spent decades locating and exhuming mass graves of people killed under Soviet dictator Joseph Stalin's rule.
Activists say the case against him is an attempt by authorities to muzzle the outspoken historian who has called attention to one of the darkest chapters in Russia's history.
Dmitriyev was arrested in late 2016 and spent more than a year in pre-trial detention before being released in January after calls from prominent figures for him to be freed.
In April, a court acquitted Dmitriyev of pornography charges, in what Russia's liberal rights community called a rare, nearly unbelievable victory in a country where judges almost always side with prosecutors.
The historian was however found guilty of firearm possession and released on conditions that limited his freedom for the next three months.
But then Dmitriyev was detained again after a higher court overturned the "not guilty" verdict this month.
State-controlled NTV television, known for its attacks on Kremlin critics, said that Dmitriyev apparently planned to flee to Poland.
His defence lawyer denied the charge, saying the historian did not even have a passport to travel abroad.
"They are either sick or carrying out someone's order," Anufriyev said of the television channel.
Dmitriyev is known for helping open the Sandarmokh memorial in a pine forest in Karelia in memory of thousands of victims -- including many foreigners -- executed in 1937 and 1938.
"This is a desire by the prosecutors and those who ordered the case to get revenge," rights activist Zoya Svetova told AFP.
She said the cases of Dmitriyev and Ukrainian filmmaker Sentsov unfolding against the backdrop of the month-long football extravaganza spoke of Moscow's impunity.
"There's a feeling that the West is turning a blind eye to rights violations in Russia and Russia can feel it," she said.
The Kremlin has ignored multiple pleas to free Sentsov and Russia's rights ombudsman Tatyana Moskalkova compared his hunger strike to "dieting".
Sentsov was detained after Russia annexed Crimea in 2014. He was convicted of terrorism and is serving a 20-year prison sentence in Russia's far north, in what supporters say is punishment for the Ukrainian's anti-Kremlin stance.