Europol supports European national agencies

The head of EU police agency Europol, Rob Wainwright, says it is becoming extremely difficult to foil terror attacks due to the large number of radicalized Muslim extremists in Europe, their lack of command structure, and their growing sophistication.

"The scale of the problem, the diffuse nature of the network, the scale of the people involved make this extremely difficult for even very well-functioning counterterrorist agencies such as we have in France to stop every attack," Wainwright said in an interview to AP.

"Official" terror groups headed by a leader are often replaced by numerous independent or semi-independent terrorists who act on their own. It is very difficult to track them, he explained, adding that at least 2,500 and perhaps up to 5,000 Europeans are suspected to have joined militants in Syria and Iraq.

 Diffused nature of terror cells makes attack prevention 'extremely' hard – Europol