In a letter addressed to the Swedish authorities, the Hermitage Capital investment fund accused Nordea of fraud and laundering $175 million of dirty money between 2007 and 2013, it said.
Hermitage Capital's American chief executive Bill Browder is a former client of Russian lawyer Sergei Magnitski, who died in 2009 in a Russian jail after being denied medical care.
Browder, who alleges that Magnitski was killed, told the business daily Dagens Industri that “since it's not possible to prosecute anybody for the murder in Russia, we're trying to start money laundering cases in the West”.
His fund alleges that large sums originating at Lithuania's Ukio bank and Danske Bank's Estonian subsidiary transited through 365 Nordea accounts in Sweden, Denmark, Finland and Norway, and that this was “just the tip of the iceberg”.
Nordea told the TT news agency that it “systematically reports all suspicious transactions to the relevant authorities”.
It is likely that Sweden will task a prosecutor with examining the claim and deciding on whether to launch a investigation.
Browder told AFP earlier this month that “as we peel the onion of money laundering at Danske Bank the story will only get more and more sordid.”
Denmark's biggest bank, Danske Bank, has plunged into a reputational maelstrom whipped up by the alleged laundering of up to 200 billion euros ($235 billion).
The bank's investors and clients have headed for the exits amid growing fears of a possibly huge US fine for laundering funds for 15,000 mainly Russian clients.