A Moscow court on Tuesday extended until April the pre-trial detention of a historian who confessed to murdering and dismembering his ex-student lover, a grisly crime that sent shock waves across Russia.

Oleg Sokolov, a prominent expert on Napoleon based in Saint Petersburg, was hauled out of the icy Moika River in November with a backpack containing a woman's arms.

The 63-year-old was arrested for two months over the murder of his 24-year-old girlfriend and former student Anastasia Yeshchenko.

A Moscow court on Tuesday extended his detention until April.

"The court has ruled to extend the detention for three months, until April 9," Sokolov's lawyer Alexander Pochuyev told AFP.

He said the defence would decide whether to appeal later.

The next court hearing to decide whether to extend Sokolov's detention past January 8 was supposed to take place in the new year but was pushed forward because of the long holiday break in Russia, Pochuyev said.

The case -- and allegations that Sokolov had abused at least one other female student -- prompted widespread outrage in Russia and demands to address reports of domestic violence and harassment in Russian university.

Sokolov was hauled out of the icy Moika River last month carrying a backpack containing body parts
Sokolov was hauled out of the icy Moika River last month carrying a backpack containing body parts AFP / Olga MALTSEVA

Russia has no specific legislation on domestic violence or sexual harassment in the workplace and feminist movements like #MeToo have had little impact in the country.

Sokolov was earlier transferred to Moscow where he is undergoing psychiatric assessment at the Serbsky State Centre, Russia's main centre of forensic psychiatry.

Pochuyev said the assessment was set to last until early January.

Sokolov, a professor at Saint Petersburg State University, is the author of several books on French emperor Napoleon Bonaparte and often led historical re-enactments of the Napoleonic war in Russia.

He received France's Legion d'Honneur in 2003.

He and Yeshchenko co-authored a number of works and liked to wear period costumes, with Sokolov dressing up as Napoleon.

He allegedly shot and killed her during an argument and then sawed off her head, arms and legs.

After disposing of the corpse he reportedly planned to commit suicide at the Peter and Paul Fortress, one of the former imperial capital's most famous landmarks, dressed as Napoleon.

Russia