The threat of a terrorist attack in the Netherlands remains at substantial, or level four out of five, counter-terrorism agency NCTV said in its latest quarterly update.

The high level of alert reflects the continuing threat of jihadi-based attacks and the way in which youngsters are becoming radicalised and adopting far-right and jihadi sympathies, the agency said.

The speed at which this is now happening is “concerning”, the NCTV said, adding that several hundred Dutch youngsters, some as young as 14, are now active in far-right and jihadi online groups.

“We live in uneasy times, and there is a lot of attention for geopolitical themes such as the Russian war of aggression in Ukraine and the tensions in the Middle East,” said national coordinator Pieter-Jaap Aalbersberg. “But we must not forget that the terrorist threat remains high.”

He also referred to the recent arrest of eight “sovereign citizens” in the Netherlands, who face legal action for terrorism offences, and some of whom were armed. This, he said, “is a relatively new phenomenon and it requires continual attention.”

“Sovereign” citizens refuse to recognise the state or rule of law and last year the NCTV put their number at least 10,000, and possibly more.

The AIVD the group forms part of a broader movement that promotes “anti-institutional extremism”, to combat a “malevolent elite” allegedly out to oppress citizens.