Fines totalling €310,000 ($392,415) were handed out to Redcorp SA (€130,000), Bluemay Enterprises NV (€130,000) and Bluemay Enterprises Ltd (€50,000) for their involvement in the unlicensed 7red.nl/.com and royaalcasino.nl/.com websites.
The regulatory body ruled that both websites have been illegally offering online games of chance in the country and also cited a number of complaints from customers.
An investigation found that although the language on the websites had been translated to English after an initial warning from the regulator, it remained focused on players in the Netherlands.
The regulator also found that both websites had promoted their services to Dutch players via a number of television channels.
In addition to handing out fines, the regulatory body issued personal warnings to a number of people involved with the illegal services.