A Russian court on Friday denied granting parole to former Yukos oil tycoon Mikhail Khodorkovsky, news agencies reported.

Khodorkovsky, 45, once Russia's richest man, applied for parole having served over half of an eight-year jail term for large-scale tax evasion charges against his former oil empire Yukos.

"The court ruled to deny parole and the decision can be appealed within 10 days," Judge Igor Falilyev said in the Siberian town of Chita, where Khodorkovsky is jailed.

Falilyev explained his refusal by saying Khodorkovsky had neglected to take sewing classes while in detention and cited an alleged misdemeanour from October.

Khodorkovsky's defence lawyer Vadim Klyuvgant denounced the decision as having "no relation to the law."

"The first reason is that Khodorkovsky failed to learn the profession of a sewing machine operator ... The second is a reprimand issued on October 15, 2007 by the prison administration for failing to comply with an order to put his hands behind his back," Klyuvgant was quoted by news agency Ria-Novosti as saying.

Khodorkovsky and his business partner Platon Lebedev have claimed that the case against Yukos was politically orchestrated by former president Vladimir Putin to sideline Khodorkovsky as a political opponent and to absorb back into state hands the energy company's mighty assets.

Khodorkovsky's lawyers filed for parole on July 16, saying their hopes were based on President Dmitry Medvedev's more clement rhetoric and promises to fight against "legal nihilism" since he took office in May.

But as Khodorkovsky left the courtroom cage in handcuffs, he told a Ria-Novosti reporter: "The judicial system won't be reformed any time soon."

Had the Chita court granted Khodorkovsky parole, he would have remained in pre-trial detention on new charges of embezzlement and money laundering filed against him in June.

In his parole appeal Thursday, Khodorkovsky vowed to dedicate his life to charity and to stay out of business.

"Upon my release, I am not going to return to the oil and gas business and seek a revision of unjust decisions concerning Yukos," he was quoted as saying in a statement released by his lawyers. "I intend to devote myself to humanitarian projects and, most importantly, to be a family man."

Analysts point to the Yukos case as the beginning of Putin's drive to extend the Kremlin's hand over the lucrative oil sector.

State firm Rosneft, chaired by Putin's former chief of staff Igor Sechin, gobbled up the bulk of Yukos' assets in a forced bankruptcy auction, allowing it to grow into the country's largest oil firm.