A Russian regional court reversed on Friday a lower court’s decision to reduce the sentence of Platon Lebedev, the former business partner of jailed oil tycoon Mikhail Khodorkovsky.

In August a court reduced Lebedev's sentence from 13 years to nine years and eight months.

The case has now been sent back to a lower court for further consideration.

The two men have been in jail since 2003, having been convicted of fraud and tax evasion at two trials in 2005 and 2010. Both trials have been widely criticized abroad. They maintain that the prosecution against them has been politically motivated, a claim denied by Russian authorities.