Russian prosecutors have presented money-laundering and embezzlement charges against Mikhail Khodorkovsky, the former oil tycoon's lawyer has said.
Khodorkovsky, a Kremlin opponent and formerly Russia's richest man, is already in prison after being found guilty of fraud.
Karinna Moskalenko, his lawyer, said on Monday: "Embezzlement and money-laundering charges were presented today... The sums they are talking about are in the tens of billions of dollars.
"It's an absurd accusation."
A trial could start in the Siberian city of Chita this week, she said.
Khodorkovsky, founder of the now-bankrupt oil giant Yukos, has been serving an eight-year sentence after being convicted in 2004 on fraud and tax evasion charges following a politically charged trial.
His former associate, Platon Lebedev, is also serving an eight year jail term having faced the same charges in 2004.
The Interfax and ITAR-Tass news agencies have quoted Lebedev's lawyer as saying that his client also faces fresh fraud charges.
Political threat
Prior to Khodorkovsky's arrest and the parallel tax inquiry that saw most of Yukos transferred to a state company, the businessman was estimated by Forbes magazine as having a fortune worth $15bn.
The case was widely seen as a Kremlin-driven vendetta after Khodorkovsky funded opposition parties, as well as a means for the state to regain control of a chunk of the strategically important oil sector.
Khodorkovsky could now face up to 15 years for money-laundering.
He has been in detention since October 2003 and could be eligible for parole later this year.
Kremlin critics suggested that the new charges were aimed at ensuring he remains in prison and presents no political threat.
Prison terms on separate charges are not usually served consecutively in Russia; convicts are jailed for the longest sentence.