A Dutch security official meant to protect a far-right politician has been arrested on suspicion of leaking his location to a Moroccan criminal gang.
Dutch populist Geert Wilders - who called some Moroccans "scum" last week - told Prime Minister Mark Rutte the alleged breach was "unacceptable".
Police said the man was of Moroccan descent but not a bodyguard.
Opinion polls suggest Mr Wilders' Freedom Party will emerge as the most popular in next month's election.
- Why Dutch populist Geert Wilders is scenting victory
- Are Dutch voters really turning to Wilders?
The officer from the DBB security team was detained on Monday for "sharing classified police information in the private sphere", police spokesman Dennis Janus confirmed to the Associated Press news agency.
The DBB is responsible for security around the Dutch royal family, diplomats and high profile politicians, like Mr Wilders, based in the Netherlands.
Local media, citing security sources, said the information was being passed to a Dutch-Moroccan gang.
Mr Wilders has been under 24-hour police protection for more than a decade, due to death threats.Image copyright EPA Image caption It is alleged the official leaked information about Mr Wilders' whereabouts
But National Police Chief Erik Akerboom told a Dutch radio station he did not believe Mr Wilders' safety had been compromised, as the officer was not part of the inner circle protecting the politician.
However, Mr Wilders, who was found guilty of hate speech over his promise to reduce the number of Moroccans in the country last year, tweeted: "If I can't blindly trust the service (DBB) that has to protect me, I can no longer function. This is unacceptable."
Mr Wilders' Freedom Party is expected to do well in Dutch parliamentary elections, but other mainstream parties say they will not join a coalition with the group due to its anti-Islam stance.