THESSALONIKI, Greece (AP) — Police clashed with protesters and detained more than 30 people in Greece’s second-largest city Monday during a demonstration against a new campus security law.

Protesters occupied the principal’s building at the University of Thessaloniki in northern Greece for several hours and the clashes broke out when police entered the building to remove them.

Parliament earlier this month approved legislation from the center-right government allowing police to patrol university campuses. Left-wing opposition parties have called the measure undemocratic and have supported ongoing protests against the new measures.