Smuggling networks cashing in on the huge flow of migrants into Europe had an estimated turnover last year of up to $6-billion (U.S.), international law enforcement agencies said Tuesday.

They said that the number of people trying to reach the European Union is expected to increase, with some 800,000 waiting in Libya to cross the Mediterranean. More than 1.2 million people applied for asylum in the EU last year.

A summary published Tuesday of a joint Europol and Interpol report also warned: "There is an increased risk that foreign terrorist fighters may use migratory flows" to sneak into Europe. It noted that two extremists involved in the deadly rampage in Paris on Nov. 13 last year entered the EU through Greece as part of the influx of migrants from Syria.

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Europol said an estimated 90 per cent of all migrants entering the European Union have their trip facilitated by smugglers, sometimes helped by corrupt officials paid off to ensure boats are released and vehicles allowed to pass borders.

Europol Director Rob Wainwright said the report "describes the huge role played by organized-crime networks in the migration crisis and sends a clear message to the EU and its member states that we must combat these networks in the strongest possible terms."

The report was drawn up following a meeting earlier this year of law-enforcement officials in The Hague and is intended to help shape future crime-fighting strategies.

It says the turnover of smuggling networks likely was $5-6 billion based on the number of arrivals last year who were helped by smugglers and how much the migrants paid — an average of $3,200-$6,500 per person.