Interpol says it has detected more than a dozen suspected «foreign terrorist fighters» crossing the Mediterranean Sea during a six-week operation.
The international police organisation carried out more than 1.2 million searches at ports in six countries between 24 July and 8 September.
Operation Neptune II focussed on busy tourist routes between North Africa and southern Europe. It resulted in 31 active investigative leads, Interpol says.
In a separate development, France and Italy called for a new system to automatically redistribute migrants across the EU as the number of people entering Europe surged. The current system, French President Emmanuel Macron said, was particularly unfair on Italy.
Only this week, hundreds of migrants arrived in Italy and Greece, many travelling by boat from Libya and Turkey.