Jailed former Yukos CEO Mikhail Khodorkovsky may be investigated for money laundering, a German news report said.

A money-laundering case against Khodorkovsky was opened in Germany several months ago, Sueddeutsche Zeitung reported Saturday. The paper did not say whether the case was still open.

German investigators accidentally found accounts under Khodorkovsky's name worth between 15 million euros and 20 million euros ($20 million to $27 million) during a tax evasion raid, the report said. The details of the account, found on a CD-ROM containing data of Swiss private bank Julius Baer, may be evidence that Khodorkovsky did not pay taxes.

Khodorkovsky is serving a 13-year sentence in a prison in Karelia on tax evasion, fraud and money-laundering charges that he and his supporters call politically motivated punishment from Prime Minister Vladimir Putin for his political and commercial ambitions. The prison sentence stems from two trials, one in 2005 and the other in 2010.

While the European Court of Human Rights has cleared Russia of political motivation in the first trial, it has ruled the Yukos trial unfair.

A money-laundering case would deal a blow to human rights activists who have rallied around Khodorkovsky, said Alexander Rahr, a Russia expert with the German Council of Foreign Relations.

"An investigation would be a shock for those who said the money-laundering [charge] was Putin's fantasy," Rahr said.

He expressed surprise that there was not more money in the account, calling the balance "funny."

Khodorkovsky's head lawyer Vadim Klyuvgant, speaking by phone Sunday, called the media report a rumor and said he knew nothing about any German investigation.

Khodorkovsky's press service declined to comment by phone Sunday.