Up to 5,000 European Union citizens have joined jihadist militant ranks, the head of European police agency Europol told British lawmakers today.
"We're talking about 3,000, 5,000 EU nationals," Rob Wainwright told a parliamentary committee when asked how many foreign fighters had left from Europe.
"We're dealing with a large body of mainly young men who have the potential to come back and have the potential or intent and capability to carry out attacks we have seen in Paris in the last week," he said.
Wainwright also called for greater scrutiny of the use of social media by jihadist groups.
"We have to have a closer, much more productive relationship between law enforcement and technology firms.
"One of the important evolutions we're seeing right now in the current terrorist threat is the way the Internet is used, clearly much more aggressively, much more imaginatively by the networks," he added.
The European Union's counter-terrorism chief Gilles de Kerchove estimated in September 2014 that around 3,000 European citizens had joined jihadists in Syria and Iraq.
De Kerchove said that around 30 per cent have returned to their EU countries.
