A prominent Saint Petersburg-based Napoleon expert has confessed to murdering his young lover and former student after he was hauled out of the icy Moika River with a backpack containing a woman's arms.

Key points: Sokolov was reportedly drunk and trying to dump body parts in the river when he fell in

Sokolov was reportedly drunk and trying to dump body parts in the river when he fell in He told investigators that he shot and killed his lover during an argument

He told investigators that he shot and killed his lover during an argument Both he and his lover liked to wear period costumes, with Sokolov dressing up as Napoleon

Oleg Sokolov, a 63-year-old history lecturer who received France's Legion d'Honneur from Jacques Chirac in 2003, was arrested on Saturday on suspicion of murder in a grisly crime that sent shockwaves across Russia.

"He has admitted his guilt," Sokolov's lawyer Alexander Pochuev said, adding he regretted what he had done and was cooperating.

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Sokolov was reportedly drunk and fell into the Moika, a tributary of the Neva, in central Saint Petersburg as he tried to dispose of body parts near the offices of investigators.

After killing Anastasia Yeshchenko, 24, he reportedly planned to take his own life at the Peter and Paul Fortress — one of the former imperial capital's most famous landmarks — dressed as Napoleon.

Sokolov teaches history at Saint Petersburg State University, President Vladimir Putin's alma mater, and was close to Russian authorities.

He told investigators he shot and killed his lover during an argument and then sawed off her head, arms and legs, local media reported.

Mr Pochuev suggested Sokolov may have been under stress or emotionally disturbed.

Police searched his home and discovered a blood-stained saw and the decapitated body of Yeshchenko, with whom Sokolov had co-authored a number of works.

A 'freak' who called his lover 'Josephine'

The historian, who also taught at the Sorbonne, is the author of books on French emperor Napoleon Bonaparte.

He acted as a consultant on several films and took part in historical re-enactments of the Napoleonic wars.

Both he and his lover studied French history and liked to wear period costumes, with Sokolov dressing up as Napoleon.

Students described Sokolov as both a talented lecturer who could impersonate the French emperor and his generals and a "freak" who called his lover "Josephine" and liked to be addressed as "Sire".

Many expressed dismay, saying Sokolov had long been known for his hostile behaviour but officials had ignored complaints.

Vasily Kunin, who studied with the victim, blamed university management.

"They did not pay attention to certain things," he said. "There was a policy of hushing things up."

Sokolov acted as a consultant on several films and took part in historical re-enactments of Napoleonic wars. ( AFP: Petras Malukas )

Russian media said Sokolov had also beaten up and threatened to burn with a hot iron and kill another female student in 2008 but was never charged.

More than 800 people have signed a petition calling on authorities to punish the Saint Petersburg State University leadership.

"What happened is simply monstrous," a Saint Petersburg State University lecturer said.

Speaking on condition of anonymity, he said Sokolov was dedicated to his work but was also emotionally unstable and abused alcohol.

Screenwriter Andrew Ryvkin said Sokolov was one of his lecturers, describing the Saint Petersburg-based university as a place where "alcoholics" and "anti-Semites" felt at ease.

His former student, Fyodor Danilov, said Sokolov was regarded as one of the university's best lecturers but also an eccentric man who at times yelled in French.

A spokeswoman for the Grand Chancery of the Legion of Honour indicated Sokolov might be stripped of his award.

Sokolov was also a member of Lyon-based Institute of Social Science, Economics and Politics (ISSEP), which announced on Saturday that he had been stripped of his position on its scientific committee.

AFP