THESSALONIKI — Riot police in this northern Greek city fired tear gas to disperse crowds attacking them with gasoline bombs and stones late Thursday during a protest against government plans to introduce policing on university campuses.

About 5,000 members of left-wing and anarchist groups took part in the march through the center of Thessaloniki, with some smashing shop windows and setting rubbish bins on fire. At least eight people were detained. No injuries were reported.

Earlier in the day, protesters faced off with police at the city’s main state university campus, where unrest has been bubbling for weeks over a left-wing sit-in that was closed down. Officials are trying to build a new library where the squat was, and police are there to guard construction workers from attacks by people angered by the ending of the sit-in.

Protesters are angry at government plans to introduce a new police body to guard university campuses, which lack effective private security and have suffered from political violence as well as petty crime.

Greece’s center-right government has scrapped decades-old laws that effectively prevented police — in the name of protecting academic liberties — from entering university grounds in most circumstances.

Left-wing opposition parties strongly criticized that move as well as the planned campus police, who are expected to assume duties in coming weeks.

Three arrests after student protest over campus police in Thessaloniki; one officer injured

Nine people were detained, of which three were formally placed under arrest, following violent incidents that broke out in Thessaloniki on Thursday after a march by students and anti-authoritarian groups protesting against the presence of police on university campuses, the Hellenic Police announced.

One police officer was injured during the protest.