Russia's Supreme Court has reduced former oil tycoon Mikhail Khodorkovsky's jail sentence by two months, his legal team has said.
The court on Tuesday cut the sentence of Khodorkovsky and his business partner Platon Lebedev to 10 years and 10 months from 11 years.
This means Lebedev should now be released in May 2014 and Khodorkovsky in August 2014, the Interfax news agency said.
Khodorkovsky, 50, who was Russia's richest man as head of the Yukos oil company before his arrest in 2003 and sentencing in 2005 for tax evasion and fraud, read out his appeal in a video link from a prison colony near the Arctic Circle.
"In this case, the usual mantra that everything is legal and well-grounded just won't do," Khodorkovsky, seen by some Kremlin critics as a potential opposition leader, said, reading from notes clearly and calmly.
The Moscow-based court opened to assess whether his second sentence for money laundering and embezzlement should be lifted before he is due to walk free in October 2014.
Khodorkovsky's defence team argued in the appeal that he and his business partner Platon Lebedev were convicted in 2010 on charges that were known to be false and that were invalid from the start.
Khodorkovsky denounced what he said was the use of Russian prosecutors and investigators as an "instrument of domestic politics in Russia".
"The result is catastrophic," said Khodorkovsky, who was shown on the video speaking behind a mesh grill wearing his laminated prison identity card.
In a surprise decision in May, the Supreme Court agreed to hear the appeal, which was submitted in March.
Prosecutors on Tuesday had asked the court not to shorten the sentences of Khodorkovsky and Lebedev.
Russian president Vladimir Putin, who has never made a secret of his dislike of Khodorkovsky, said even before the verdict in the second trial was announced that "a thief should be in prison," drawing criticism that he was interfering in the process.