Khodorkovsky has been imprisoned since 2003 and is set to go free in 2014. But his supporters have long feared the authorities would impose new charges to keep him in prison indefinitely.

Deputy general prosecutor Alexander Zvyagintsev told the Interfax news agency in an interview that Khodorkovsky was unlikely to benefit from a planned presidential amnesty this year.

“There are several criminal cases under investigation involving him and several other people, which have a good chance of making it to trial,” said Zvyagintsev, Interfax reported.

Zvyagintsev appeared to indicate that it was highly unlikely that Khodorkovsky, who has been convicted of tax evasion and embezzlement in two highly controversial trials, will have a chance for the amnesty now mooted in the Kremlin.

“Khodorkovsky has been convicted and is serving a sentence according to a court verdict for especially heavy crimes, done in an organised group. You make your conclusions from that,” he said.

He gave no indications on the nature of the other cases against the ex-tycoon. Usually, the opening of criminal cases over serious crimes is announced by Russia’s Investigative Committee, its equivalent of the FBI.

‘$10 billion money laundering’

Interfax also quoted a “knowledgeable source” who said the new case involves money laundering allegations.

“It has to do with the investigation of laundering outside of Russia of over $10 billion, which was stolen by the former owner of Yukos Mikhail Khodorkovsky and other persons.”

“The status of Khodorkovsky in these probes has not been determined, he is not a suspect nor has he been charged, but all that is a question of time,” the source said.

Khodorkovsky’s lawyer Vadim Klyuvgant said the defence has no information about additional criminal cases against the former owner of Yukos, who has lately been serving his sentence in a penal colony in Karelia, a northern region bordering Finland.

In May, top economist Sergei Guriyev announced he has fled Russia after investigators interrogated him as a witness in connection with the Khodorkovsky case.

He and other experts reported facing pressure after writing a report for the Kremlin human rights council which concluded that the tycoon’s second conviction was unjust. Some of them feared a third Khodorkovsky case was in the making.

Another author of the report, retired Constitutional Court judge Tamara Morshchakova, told AFP at the time that investigators claimed the report was financed with “foreign money” by Khodorkovsky himself.

Once Russia’s richest man, Khodorkovsky was arrested in October 2003 and convicted of fraud and tax evasion two years later. A second trial ended in 2010 with an embezzlement conviction.

The 50-year-old is due to be released in August 2014.

Human rights activists had hoped that the amnesty, set to be announced on December 12, would release people charged or convicted of non-violent crimes and seen as political prisoners.

President Vladimir Putin said this week that the amnesty would not include people who committed “serious crimes”.

The European Court of Human Rights this year ruled that Khodorkovsky’s first charges had a “sound basis” but that his trial was unfair, ordering the Russian authorities to pay damages.