A former museum director who has conducted research at a mass grave containing the remains of thousands of people shot under Soviet dictator Josef Stalin has been convicted of having sex with a minor and sentenced to nine years in prison.

Sergei Koltyrin, who was convicted and sentenced along with co-defendant Yury Nosov on May 27 by a court in the Karelia region town of Medvezhegorsk in northwestern Russia, is the second historian involved in research at the Sandarmokh mass grave site to be prosecuted on charges related to the alleged sexual abuse of minors.