6 November 2015, 06:06 GMT
SOCHI (Sputnik) — The fighters pose serious threat to their home countries upon their return either by carrying out terrorist attacks or by recruiting and radicalizing people, Boillat added.
"Today there are more than 25,000 of these foreign terrorist fighters, who have come from more than 100 countries around the world. Among this 25,000 individuals, 6,000 are European," Boillat told the seventh regional conference of the International Association of Prosecutors for Central and Eastern Europe and Central Asia.
The Islamic State jihadist group is notorious for using all available means of propaganda to recruit foreigners. The group controls large territories in Syria and Iraq, expanding its influence to other countries in the Middle East and North Africa.
