Former Russian opposition leader Alexei Navalny was killed with a punch to the heart, a technique by ex-KGB special forces agents, after being exposed to freezing conditions for several hours.
The Times writes quoting Vladimir Osechkin, founder of the human rights group Gulagu.net.
Meanwhile, his collaborators have announced that next month the Far North Russian court will examine a complaint filed by Navalny's mother, who is prevented from seeing the body of his son.
Lyudmila Navalnaya traveled to the remote IK-3 prison where her son died, but since Saturday, when she arrived, she has been barred from seeing his body.
According to the Tass news agency, the court has received a complaint for "illegal acts" and the hearing will take place behind closed doors.
The court in the Arctic city of Salekhard will hear the case on March 4, officials said.
Reproduction reserved © Copyright ANSA