According to the NL Times newspaper, the unrest began after a brawl in the event pavilion. Its participants threw stones, bicycles and road signs at the police, and set two law enforcement vehicles on fire.
Police dispersed people using tear gas with the approval of the city's mayor, Jan van Zanen. He instructed to introduce a state of emergency in the area of the incident.
Earlier, a rally of thousands in support of Palestine was held in the center of Athens.
In France, protesting farmers started a fire at a customs office in the southern commune of Nimes.