The PJ said that Operation Kryptonite, as it is known, was overseen by its National Anti-Corruption Unit and included seven searches.

The detainees had, it explained, set up front organisations and opened accounts in financial institutions in Portugal.

The group, of a "transnational nature," moved millions of euros through Portugal, the police added.

The PJ continues to investigate to determine the nature and scale of the criminal activity in question.