Several thousand people rallied in central Ljubljana on Tuesday to protest against government measures and the introduction of Covid certificates.
The police used water cannon and tear gas to disperse the protesters after the rally turned into rioting, and managed to calm the protest late in the evening.
According to media reports, the police arrested Zoran Stevanovic, a politician from Kranj who had spoken against the government at several previous rallies. He is considered by the police to be one of the organizers of the protest.
Since an informal EU-Western Balkans summit is taking place in nearby Brdo pri Kranju, and following announcements that protesters might try to get closer to the heads of state or government on Wednesday to gain visibility, the police have stepped up security there as well.