Police in three European countries have busted an Internet gang suspected of stealing millions of euros by diverting money to illegal online accounts, justice officials said on Wednesday.

Italian, Spanish and Polish police on Tuesday arrested 49 people suspected of running a so-called "man-in-the-middle" scheme, stealing six million euros ($6.7 million) from people and businesses across Europe, Eurojust said in a statement.

Criminals "insert" themselves in transactions between parties, pretending to be legitimate receivers of online payments but they then divert the money into their own bank accounts.

"The suspects, mainly from Nigeria and Cameroon, transferred the illicit profits outside the European Union through a sophisticated network of money laundering transactions," said the Hague-based Eurojust.

The police operation was coordinated by Europol with Belgian, British and Georgian support, it added.

"Yesterday's action against cybercriminals yielded excellent operational results and demonstrated that several EU bodies and national authorities, joining forces, can together successfully combat one of the most difficult to detect forms of modern criminality," Eurojust said.