“Drug sales on these markets, although modest when compared to the overall retail drug market, are signifiant and appear to be expanding,” the report said.

Presented in Lisbon, the report by the European Union’s law enforcement agency Europol and it drugs agency, the European Monitoring Center for Drugs and Drug Addiction (EMCDDA), said illicit substance trafficking accounted for two-thirds of exchanges made on the encrypted darknet.

Europol director Rob Wainright said strengthened intelligence sharing in Europe would be critical in fighting the suppliers.

European suppliers, particularly in Germany, the Netherlands and the United Kingdom, account for about 46 percent (about 80 million euros, or $95 million) of sales on the 16 major darknet markets analysed from 2011 to 2015.

The dynamic nature of the online markets and the ability of traffickers to evolve against efforts to shut them down mean it is crucial for authorities to keep pace, the report said.

“In just a few clicks, buyers can purchase almost any type of drug on the darknet, be it cannabis, cocaine, heroin or a series of new substances,” EMCDDA chief Alexis Goosdeel said.

“This poses a growing threat to the health and security of citizens.”

Dimitris Avramopoulos, European Commissioner for Home Affairs, said the EU was “boosting our efforts to fight illegal drugs and step up cybersecurity”.