Rock musician Andrei Makarevich, writer Lyudmila Ulitskaya, actors Chulpan Khamatova, Lia Akhedzhakova, and Aleksandr Filippenko, and Soviet-era dissidents Pavel Litvinov and Yuly Kim expressed their support for Dmitriyev, calling for his immediate release at an event held by the Memorial human rights center on the premises of the Andrei Sakharov Center in the Russian capital on May 29.

Relatives of gulag victims who took part in the event via the Internet shared their stories and expressed their gratitude to Dmitriyev for finding the sites where their loved ones were executed and/or buried.

The event was followed online by more than 10,000 people.

Dmitriyev's lawyer, Viktor Anufriyev, said at the event that his client faced pressure from several cellmates, who tried to force him to confess and Dmitriyev had to alert the detention center's administration.

According to Anufriyev, Dmitriyev was subsequently transferred to another cell.

Dmitriyev, 62, is the chief of the Moscow-based human rights group Memorial's branch in Karelia, which border Finland. He has worked for decades to expose crimes committed in the region by the Soviet state under dictator Josef Stalin, which have met with opposition under Russian President Vladimir Putin.

Dmitriyev was arrested in 2016 on child-pornography charges based on photographs of his foster daughter that authorities found on his computer.

But he testified that the photos were taken because medical workers had asked him to monitor the health and development of the girl, who was malnourished and ailing when Dmitriyev and his wife took her in as a foster child.

His supporters said the case was brought against him because he exposed a side of history that complicates the Kremlin's glorification of the Soviet past.

A local court acquitted Dmitriyev in April 2018, but the Karelia Supreme Court upheld an appeal by prosecutors and ordered a new trial.

The historian was rearrested in June 2018 and is currently on trial on the more severe charge of "violent acts of a sexual nature committed against a person under 14 years of age" -- again referring to his daughter.