The trial of 34 people involved in blocking a motorway to prevent anti-Zwarte Piet demonstrators reaching the Frisian town of Dokkum will take place in October, judges said at a pre-trial hearing on Friday.

The public prosecution department says the Piet supporters put road safety at risk by blocking off the motorway with cars and other vehicles. In addition, they prevented others from making use of their legal right to demonstrate, the department said.

The 34 people, aged between 20 and 16, stopped buses carrying some 120 demonstrators by braking in front of them on the highway, forcing all traffic to a halt.

The action led to the demonstration being cancelled by the mayor on public order grounds even though the demonstrators had been given a licence to protest during the arrival of Sinterklaas.

No-one was arrested during the stand-off.