"The court has extended custody of Khodorkovsky," Marina Savvateyeva said, adding that the once richest man in the country had "accepted the court's decision very calmly."
Khodorkovsky is currently serving an eight-year prison term for fraud and tax evasion. He has consistently denied all charges against him, saying he was punished for supporting the country's pro-Western opposition, and that the subsequent liquidation of Yukos was engineered by corrupt government officials aiming to seize lucrative oil assets.
The founder of what was once the country's largest oil company was arrested in October 2003 and convicted in May 2005. Earlier this year new charges of laundering $28.3 billion and stealing huge volumes of oil between 1998 and 2004 were filed against him.
Khodorkovsky appealed in September against a lower court's August 22 decision to deny him parole. The head of the Federal Penitentiary Service later said that a court decision on granting parole could only be made six months after the court's previous ruling on the issue.
Former Yukos executive Leonid Nevzlin was sentenced in absentia in August to life imprisonment by a Russian court.
Investigators say that between 1998 and 2002, members of an organized criminal group led by Nevzlin murdered, among others, the mayor of Nefteyugansk, where Yukos's main production unit was based, and businesswoman Valentina Korneyeva.