THESSALONIKI, Greece — Extensive clashes broke out between police and protesters Thursday in Greece’s second-largest city, Thessaloniki, after authorities ended an occupation by students and other demonstrators at the city’s main university building.

Protesters threw petrol bombs at police after street clashes erupted near the city center. Police responded with tear gas and made multiple arrests. No injuries were reported.

The occupation, which had lasted for about three weeks, was to protest a decision by the center-right government to start police patrols of university campuses.

Despite lockdown restrictions, dozens of protest marches have taken place in Greek cities over the past month against the prospect of police gaining access to campuses.