Oleg Sokolov, a 63-year-old history professor at St Petersburg State University known for re-enacting Napoleonic battle scenes, confessed in court on Monday to shooting dead Anastasia Yeshchenko, a 24-year-old postgraduate, with a rifle.

Sokolov told the court he had loved Yeshchenko and that they had been lovers for five years. But they argued over his children from another relationship and he had "lost control", shooting her four times with a sawn-off rifle, he said.

"During the row, we all lost control. I don't understand how it happened. Something like this has never happened to me before. She attacked me with a knife," he was quoted as saying by the Interfax news agency.

"I repent," he said.

Investigators suspect Sokolov, whose expertise on Napoleon Bonaparte earned him a Legion of Honour order of merit from France, of chopping his lover into pieces and of trying to dump them in the river to cover his tracks.

He was hauled from the Moyka River on Saturday morning with a rucksack containing a gun that fires rubber bullets and the dismembered arms of a woman, Russia's Investigative Committee, which handles major crimes, said in a statement.

He was treated for hypothermia.

Divers have been combing the river for Yeshchenko's remains but instead found the skeleton of a man, a find apparently unrelated to the historian's case.

Yeshchenko's remains may have been swept out by currents into the Gulf of Finland, the search team was cited by the RIA news agency as saying.

Sokolov appeared in court on Monday and was visibly upset, occasionally holding his head in his hands as he spoke to his lawyer.

Sokolov's lawyer Alexander Pochuyev said his client had probably been sober during the murder.

The court ruled to hold Sokolov in pre-trial custody for two months.

Australian Associated Press