Berlin: Europol director Rob Wainwright admitted on Saturday that there are "great concerns" about the Euro football championship to be held in France in June as it will be "an attractive target for terrorists". In an interview with German newspaper Die Welt, Wainwright recalled the latest attacks on cafes, restaurants and concert halls in Europe, saying that guarding these areas poses massive challenges for security forces, reports Efe. He noted that it is "absolutely necessary" to strengthen counter-terrorism units to deal with these new scenarios, which could include hostage-taking, such as in the Bataclan attack in Paris last November. Security forces currently have information on nearly 5,000 people who have joined the Islamic State group in Syria and Iraq as foreign fighters, and one-third of them have returned to Europe. But according to Wainwright, it is "impossible" to monitor all potential terrorists 24 hours a day. Wainwright stressed that European countries need to cooperate to fight terrorism, exchange information and carry out joint investigations.