Kerimov, who in April was ranked Russia's eighth-richest person with a fortune of $18.4 billion, is invested in European banking stocks, which have been battered by the global credit crunch.
The Dagestani businessman, a Federation Council member for his native republic, was reported to have bought a stake of up to 3 percent in Deutsche Bank and a $500 million stake in Belgian-Dutch Fortis Group.
Fortis was partially nationalized after just averting bankruptcy in September. Its shares are currently trading 95 percent lower than at the start of the year.
"He sold out of Gazprom and Sberbank in the late spring, which was smart, but invested the proceeds in Deutsche Bank, Fortis and others, which was not," the source said, speaking on condition of anonymity due to the sensitivity of the issue.
The comments confirmed a report Tuesday in the German daily Handelsblatt that cited a banking source in London.
Kerimov's investment vehicle, Nafta-Moskva, said Tuesday that it did not have a press office and that no one was available for comment.
Nobody picked up telephones at Kerimov's office in the Federation Council.
Many of the country's billionaires have been hit hard by the worst financial crisis since the 1998 default.
A recent survey compiled by Bloomberg said the top 25 business leaders have lost more than $230 billion in the past five months.
A Message from The Moscow Times:
Dear readers,
We are facing unprecedented challenges. Russia's Prosecutor General's Office has designated The Moscow Times as an "undesirable" organization, criminalizing our work and putting our staff at risk of prosecution. This follows our earlier unjust labeling as a "foreign agent."
These actions are direct attempts to silence independent journalism in Russia. The authorities claim our work "discredits the decisions of the Russian leadership." We see things differently: we strive to provide accurate, unbiased reporting on Russia.
We, the journalists of The Moscow Times, refuse to be silenced. But to continue our work, we need your help.
Your support, no matter how small, makes a world of difference. If you can, please support us monthly starting from just $2. It's quick to set up, and every contribution makes a significant impact.
By supporting The Moscow Times, you're defending open, independent journalism in the face of repression. Thank you for standing with us.
Remind me later.