Up to 5,000 Europeans joined jihad, Europol chief says

“We are dealing with a large body of mainly young men that have the potential to come back, and have the intent, if not the capability, to carry out attacks that we have seen in Paris last week”, said Wainwright.

Europol has collected “about 2,500 names of suspects”.

Wainwright stressed that Syria and Iraq are not the only places where European foreign fighters radicalise.

“The problem that we are dealing with these days is not just about Syria and Iraq. It's also about other conflict zones … in Africa, in the Arab peninsula.”

On Wednesday (14 January) Al Qaeda in Yemen claimed responsibility in a video message for last week's murders at the office of Charlie Hebdo in Paris.

“While quite rightly security services around Europe have indeed been prioritising their work in dealing with the foreign fighters that return from Syria and Iraq, what the events in Paris last week show, is that there are also a threat clearly from sleeping networks," said Wainwright.

The two attackers in Paris were on a US no-fly list, yet were able to carry out their attack, prompting one MP to ask Wainwright Tuesday whether it is possible to follow every suspect ever flagged.

“It is exceptionally difficult, given the scale of the problem … for the security authorities to monitor all potential threats. That's the very painful reality that the attacks in Paris have shown,” said Wainwright.

European countries each have their own indicators to express the threat level. When asked to paint a picture of what the threat looks like across Europe, Wainwright said the threat level is higher than ever since the 2001 attacks on the United States.

“To put it in to context, it is certainly the most serious terrorist threat Europe has faced since 9/11 for example.”

The Europol chief said the current threat is “more diffuse in nature, operating in a very decentralised way”, making counter-terrorism “more difficult, much more complex than dealing with … a core leadership of Al Qaeda ten or fifteen years ago.”

Internet area

One problem Wainwright noted is that the new generation of potential terrorist use the internet “much more aggressively, much more imaginatively”.

“The dark net area of the internet, which is home to so much of this criminal and terrorist activity ... is a huge endeavour to monitor. There has been little appreciation about the scale and difficulty involved.”

After the Paris attacks, calls for stricter control of online communications have increased in Europe.

French prime minister Manuel Valls announced on Tuesday France will tighten surveillance of the internet for jihadist communication, a day after his British colleague David Cameron said Britain's intelligence agencies should have the legal power to break into encrypted communication.

Belgian justice minister Koen Geens also wants to give agencies more power to tap online communications, Belgian newspaper Het Laatste Nieuws reported on Wednesday.

On Tuesday, the EU’s counter-terrorism coordinator Gilles de Kerchove called on the European Parliament to implement the EU passenger name records legislation, a law giving authorities access to the personal details of air passengers.