The famous Russian professor of history Oleg Sokolov confessed to killing the young mistress and determined her body after a quarrel.

Saint Petersburg media said Professor Oleg Sokolov, 63, was drunk and fell into the river when he was trying to kill off parts suspected of being a woman's arm. He was later rescued ashore and arrested on murder charges.

Police ransacked Sokolov's house and discovered the intact body of 24-year-old Anastasia Yeshchenko, with whom he had collaborated on several works. Sokolov is said to have an affair with Anastasia, who is also his former student, and seems to have murdered her with jealousy since November 7.

Sokolov told investigators that he had shot and killed Anastasia after an argument and body determination.

"He has admitted his sins," said Alexander Pochuev, Sokolov's lawyer, adding that on 10 November, the client was deeply sorry about what he had done and was cooperating with the police.

Sokolov is the author of many books on Napoleon Bonaparte. He has served as a historical advisor for many films. In 2003, he was awarded the Order of the North Big Boi Tinh by French President Jacques Chirac. Sokolov is also a member of the French Academy of Social Sciences, Economics and Politics (ISSEP), but the institute in a statement released yesterday said he was stripped of his membership.

According to colleagues and students, Sokolov is a talented but mentally unstable and alcoholic. Everyone in the school knows his relationship with Anastasia but avoids discussion because "it's her own business".

Local media reported that Sokolov assaulted and threatened to kill another woman in 2008 but was not prosecuted.