According to Russian-based media reports, investigators discovered human female arms and a gun in the backpack belonging to the man, who was later identified as a well-known professor and French history expert at a prestigious university in St. Petersburg, who dealt primarily with the Napoleonic age.
"He has admitted his guilt", Sokolov's lawyer Alexander Pochuev told AFP, adding he regretted what he had done and was now cooperating. Sokolov was hospitalized Saturday for hypothermia but was taken to a police station Sunday for questioning.
Reports said Sokolov had been given France's Legion of Honor award for his work.
It is thought that Prof Sokolov was drunk and fell into the river as he tried to dispose of the severed limbs.More news: House Republicans Request Hunter Biden Testify in Public Impeachment Hearing
Anastasia had been in a relationship with the historian, 63, when he "accidentally killed her" following an argument, according to the report which stated he had confessed to police.
Russian Emergency rescuers and police investigators conduct searches on the Moika River, in Saint Petersburg, on November 10, 2019, following the murder of a woman that implicates Russian historian Oleg Sokolov.
A historical re-enactor, Mr Sokolov has often appeared in uniforms of the Napoleonic era, and has worked as a consultant on historical reproductions for film and TV.
Both he and Ms Yeshchenko studied French history and enjoyed wearing period costumes, with Prof Sokolov dressing up as Napoleon.
TASS said the human remains belonged to another person, presumed to be a man, and that police were working to establish the identity of that person.More news: Sar Kheng: Rainsy return not blocked
In 2003, Red Star, the official newspaper of the defence ministry, gushingly described Sokolov as a "serious historian" whose works were published in France.
ISSEP announced in a statement that he had been stripped of his position on its scientific committee.
"We could never imagine that he could commit such an odious act", the institute said in a statement.
ISSEP was founded by Marine Le Pen's niece, Marion Marechal.More news: Dion Waiters Reportedly 'Overdosed' on Gummies on Team Plane, Misses Heat Game