MOSCOW (AP) _ A court in the Siberian city where oil tycoon Mikhail Khodorkovsky is imprisoned ruled Tuesday that his temporary transfer to solitary confinement earlier this year was unlawful, Russian media reported.

Khodorkovsky, the former Yukos oil company chief who is serving an eight-year term after his conviction last May in a politically charged case, was placed in an isolation cell for five days in January as punishment for possession of Justice Ministry documents on inmates' rights.

The city court in Krasnokamensk, where the prison colony is located, agreed with his lawyers' arguments that he was entitled to have the documents in his cell, saying they were not secret and had been published in the media, the Interfax and RIA-Novosti news agencies reported.

The ruling came days after lawyers for Khodorkovsky said he had been hospitalized at the prison 3,000 miles east of Moscow after another inmate slashed him in the face while he slept, and accused authorities of trying to cover up the incident.

Once rated Russia's richest man, the 42-year-old Khodorkovsky was convicted on charges including fraud and tax evasion after a trial seen as punishment for his political ambitions and part of a state drive for control of the crucial oil industry.

Yukos has been dismantled and its main production unit is now under state control.