Eleven people have been arrested in coordinated raids across Europe as part of an investigation into the darknet's second-largest counterfeit currency producer, Europol announced on Monday.

More than 26,000 counterfeit banknotes, estimated to be worth €1.3 million had been sold by the criminal group, the agency added in a statement.

The cross-border investigation was triggered in July after Portuguese police dismantled a print shop and arrested five people.

Of the 36 raids carried out last week, 27 were done in Germany with the other nine spread out across Austria, France, Greece, Ireland, Luxembourg and Spain.

Authorities recovered counterfeit euro banknotes, drugs weapons, doping substances, illegally procured medicines as well as forged documents and virtual currency.

A clandestine documents print shop was also dismantled in Germany, Europol said.

The counterfeit banknotes had been distributed primarily through the illicit platform Wall Street Market, Europol told Euronews.

Wall Street market was taken down in May by German prosecutors assisted by Europol, Eurojust and various US agencies including the Department for Justice, FBI and the Drug Enforcement Administration.

With more than 1.1 million customers' account, 5,400 sellers and 63,000 sales, it had been the world's second-largest dark web market, enabling the trade in drugs (including cocaine, heroin, cannabis and amphetamines), stolen data, fake documents and malicious software.