Interpol and its European counterpart Tuesday warned of growing concerns that radical Islamists could be using illegal people smuggling networks to sneak into Europe or even fund their attacks and activities, AFP reports.

And in a joint report unveiled Tuesday, the two police agencies said those preying on desperate refugees had raked in up to $6 billion last year. That had turned the migrant flow into one of the largest money-earners for organized crime on the continent.

"Terrorists may use migrant smugglers' resources to achieve their goals," said the report by the global police body Interpol based in Lyon and Europol in The Hague.