The threat of terrorist attacks in the Netherlands remains “substantial”, ranked at level four out of five, counter-terrorism agency NCTV said in its half-yearly assessment on Tuesday. Level four means there is a realistic chance an attack will take place.

Jihadism remains the biggest threat, the agency said, but most plots in Europe are being foiled early by security services. Several people have been arrested over the past year, including two men, one of whom is accused of being an ISIS member, over suspected plans to carry out attacks.

“The threat is high and we must stay constantly alert,” national coordinator Marc Kuipers said, adding that most attacks in Europe are being prevented through the vigilance of national and international security services.

Iran and Jewish targets
The war between the United States, Israel and Iran has increased the risk of attacks in Europe, the NCTV said, with Jewish, Israeli and American sites being targeted.

The Netherlands saw a series of attacks on Jewish and pro-Israel sites in March and April, including at a Rotterdam synagogue, a Jewish school in Amsterdam and an office complex on the Zuidas that houses the Bank of New York Mellon.

A man arrested in the US in May is accused of coordinating the attacks and of recruiting for Iran’s Revolutionary Guard.

Far-right concerns
The threat from right-wing terrorism has not changed. Arrests remain rare and mostly involve young people who make online threats without concrete plans, the NCTV said.

But the agency warned about the normalisation of far-right ideas and the growing use of terms such as omvolking (great replacement) and “remigration”, which it said create “a breeding ground for violence, fear, hatred and racism” and undermine social cohesion.

Right-wing extremists have been among those active at anti-asylum protests since last summer, some of which have ended in violence and threats against local politicians.

For the first time, the report also treats “nihilistic extremism” – a violent online youth subculture – as a separate category, warning of the growing threat it poses.