There are nearly 30,000 websites linked to the Daesh terrorist group, the EU's Counter-Terrorism Coordinator Gilles de Kerchove said in an interview published Tuesday.

De Kerchove pointed to the dangers of what he called a "virtual caliphate," underlining importance of efforts to reduce the propaganda on the internet and develop a counter narrative.

A team of 20 specialists work for the EU's law enforcement agency Europol to spot and report extremist content, de Kerchove said, adding that this team has already flagged 30,000 sites.

The anti-terrorism coordinator also expressed belief that ordinary citizens should be taught to detect and report terrorism-related content.

"I also think we must train people to detect the signs of [support or promotion of terrorism]. I have known cases of brothers, relatives, who had not noticed that their loved ones were doing badly," he said.

De Kerchove added that internet providers' concern for the privacy of their customers in the form of not collecting and preserving metadata was detrimental to the work of law enforcement institutions.