The prosecutors said in a statement that they had been following "the case very closely" for a long period "due to the very serious nature and scope of the case," and vowed to "turn every stone in this case."

The state prosecutor said it was too early to say if the investigation would result in charges. A spokesperson for the office declined to comment about any potential targets or on how long the probe might take.

A similar investigation was launched by the Office of the Prosecutor General in Estonia last week.

The probes come after Bill Browder, co-founder and CEO of investment fund Hermitage Capital, filed criminal complaints in July alleging that Danske was guilty of "gross negligence and money laundering and related offenses."

Danske Bank's Estonian operations may have been used to launder as much as €7 billion, which is more than twice as much as initially believed. The case is being investigated by Danske Bank itself, the High Court of Paris as well as the Danish Financial Supervisory Authority.

Browder, the former employer of Russian lawyer Sergei Magnitsky, also sought for a criminal investigation to be launched against 26 employees of the Estonian branch of Danske Bank who allegedly enabled the laundering of billions of dollars of dirty money through the bank, dailies Postimees and Äripäev reported.