Brussels, London- The European Union’s counter-terrorism coordinator, Gilles de Kerchove, has warned of the presence of more than 50,000 extremists, including those considered “really worrying.”

He singled out Britain as having more extremists than any other country in Europe. “The United Kingdom has identified 20,000 to 35,000 radicals,” said de Kerchove.

Of these, 3,000 are worrying for MI5, and of those 500 are under constant and special attention.

There are tens of thousands of extremists in Europe, he warned, giving a number of more than 50,000.

“We must select those who are really worrying and the most dangerous, and they should be monitored 24 hours a day, seven days a week,” the EU official said.

He also warned that European countries will suffer further attacks inspired by ISIS, saying greater measures must be taken to prevent them.

De Kerchove told Asharq Al-Awsat newspaper a few weeks ago that threats in Europe have become more complicated after the terrorist attacks in Paris, Brussels and other European cities.

Several European countries believe that the dangers of extremist attacks in the EU are increasing as ISIS continues to suffer defeats in Iraq and Syria.

They believe that some of the foreign fighters will attempt to return to EU countries.