Europol

Rik Ferguson, special advisor to Europol's European Cyber Crime Centre, says the sources of speculation about the group's involvement seem credible but adds that he has seen no conclusive evidence so far.

Authorities from at least 18 other countries have been involved and the operation is still continuing, with more arrests expected in the next few weeks, Europol said.

Most of the suspects, detained last month, are Russian nationals, according to EU law enforcement agency Europol.

Europol, the EU's policing body, worked alongside Colombian investigators to track Belvedere down in Medellín.

Europol also said a number of threats to life were prevented and a drug laboratory in Australia was dismantled.