A Russian historian whose research into Stalin-era mass graves irked the authorities has been formally charged with sexual assault following an earlier acquittal on similar charges, investigators said on Tuesday.
Respected historian Yury Dmitriyev was charged with sexual assault and faces up to 20 years in prison, if convicted, a spokesman for regional investigators, Vitaly Konovalov, told AFP.
He did not provide further details.
Dmitriyev, who heads the rights group Memorial's branch in Karelia in northwestern Russia, was in April acquitted of pornography charges and the new case against the 62-year-old came as a huge shock to the country's embattled liberal community.
The authorities' turnabout in the high-profile case of the Gulag researcher 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".
The old case centred on naked photographs of Dmitriyev's then pre-teen adopted daughter Natalya seized during a search of his home after an anonymous tip-off to police.
Now investigators accuse Dmitriyev of sexually abusing his adopted daughter between 2012 and 2016. He vehemently denies all the charges.
He was detained last week after a higher court overturned the "not guilty" verdict.
During the first case, Dmitriyev was arrested in 2016 and spent more than a year in pre-trial detention before being released after calls from prominent figures for him to be freed.
Dmitriyev 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.
Prominent rights activist Zoya Svetova called the second case against the historian an "unambiguous signal" from law enforcers.
"You think we have been defeated?" she wrote on Facebook last week, referring to what she said was the authorities' logic. "It's too early to rejoice."
Yury Dmitriyev faces up to 20 years in prison if convicted