October 25 marks 10 years since jailed former oil tycoon Mikhail Khodorkovsky was arrested by Russian authorities.
Khodorkovsky, once Russia's richest man, was eventually convicted of tax evasion and sentenced to eight years in prison.
In 2010, he was given a second prison term for money laundering and embezzlement from Yukos oil company, which he headed.
Khodorkovsky is set to be released in August, and his former business partner Platon Lebedev, who was arrested a few months earlier, is expected to be freed in May.
However, Khodorkovsky's supporters fear that new charges could be prepared to keep him behind the bars.
Critics call charges against Khodorkovsky punishment for having challenged President Vladimir Putin's dominance on Russia's political scene.
In a statement on October 25, the U.S. State Department reiterated its concerns about selective prosecution, a politically motivated investigation, and lack of respect for due process rights in Khodorkovsky's and Lebedev's cases.
PHOTOGALLERY: From Young Tycoon To Graying Inmate
Based on reporting by AP and ITAR-TASS