Greek riot police have fired tear gas and stun grenades during clashes with activists protesting an arson fire at a building used by anarchist squatters in the northern city of Thessaloniki.

No injuries were reported from the confrontation late Monday. Police said five people were detained as suspected rioters.

The clashes broke out during a march through the city to protest the fire that gutted the building, which anarchist groups say was being used to house refugees. Right-wing extremists are suspected in the arson.

The fire occurred on the sidelines of a large demonstration opposing efforts to resolve a long-standing name dispute between Greece and neighboring Macedonia. Greece has a region named Macedonia, where Thessaloniki, Greece's second-largest city, is located.

Police are investigating the arson.