Four radical “sovereign citizens” have appeared in court in Rotterdam, charged with terrorism offences and two other men have been accused of supplying them with weapons.

The four, said to be members of a group called Common Law Nederland Earth, aimed to replace the government and democratic institutions and believe that using deadly violence is legitimate, the public prosecution department said at the procedural hearing.

The four had a plan for a “violent confrontation” with local officials in Deventer and included town mayor Ron Köning as a target, the department said. They also went on training exercises to improve their self defence skills.

In April, the Dutch counter terrorism unit NCTV warned that some of the tens of thousands of people in the Netherlands, who believe in the concept of an “evil elite” and refuse to recognise the state or the rule of law, are prepared to use violence.

The warning was made in a new analysis of the phenomenon by the NCTV, police and homeland security service AIVD.

The analysis says that arms have been found in the homes of some people who consider themselves to be “autonomous”, and they have also used violence in reaction to police checks, arrests and evictions.

“There has been a rise in intimidation and threats against local politicians, officials, judges, journalists and academics, among others,” the NCTV said. “There have also been some minor violent confrontations with police and bailiffs.”

The six men in the current case were arrested this year. Two of them were caught red-handed while handing over three weapons in April and the four others were arrested in July.

On Wednesday morning, police arrested a 66-year-old woman who they say is one of the leaders of Common Law Nederland Earth.

The next hearing in the case will be on December 9.