The anniversary of a fatal police shooting triggered a new riot in Greece’s capital, with protesters occupying a university building and throwing rocks and burning garbage at police.

Police fired volleys of tear gas to disperse the youths in running street battles in the center of the capital as several thousand demonstrators commemorated the death of 15-year-old Alexandros Grigoropoulos.

The rioters smashed bank windows, overturned trash bins and set them alight as they hurled rocks and fire crackers at riot police. Authorities said 177 people were detained for public order offenses in Athens and another 103 in the northern city of Thessaloniki, where a similar demonstration turned violent.

Police also clashed with protesters in the southern city of Patras and the northwestern city of Ioannina.

At least five protesters and 16 police were injured in the violence, police said.

Police on motorcycles chased rioters amid scenes of chaos at Athens’ main Syntagma Square, with youths punching and kicking officers pushed off their bikes. One policeman who lost control of his motorbike struck and injured a female pedestrian, who was tended to by demonstrators until an ambulance arrived to transport her to a hospital.

Riot police with gas masks and shields faced off against about 200 demonstrators, some of whom attacked and injured the dean of the University of Athens following a protest march Sunday afternoon, authorities said. The protesters were holed up inside and around the school’s administration building.

The university’s dean, Christos Kittas, was in intensive care after being attacked, and 16 police officers were injured, Greek authorities said.

At one point, both sides halted their confrontation to let an elderly man on a motor scooter pass between their lines — only to resume the melee once he was gone.

Skirmishes between police and demonstrators continued past nightfall, but some of the demonstrators were dispersing.

Protests began Saturday night to commemorate the December 2008 killing of 15-year-old Alexandros Grigoropoulos, whose death at the hands of police sparked rioting at the time by young self-styled anarchists across Greece. Police said they had made more than 230 arrests since the demonstrations began.

Sunday’s protest march drew several thousand people and was generally peaceful, but a few hundred — including some children — broke off from the march to occupy the university campus.

In Thessaloniki, Greece’s second-largest city, youths threw gasoline bombs at police, set fire to several cars and smashed 10 storefronts, including a Starbucks cafe.

In a newspaper interview published Sunday, Grigoropoulos’ mother, Jina Tsalikian, described her son as a quiet and friendly boy who stayed away from demonstrations.

“Before his death, Alexandros was just a kid like all the others. But now he has become a symbol of the children of his generation,” Tsalikian told the weekly Veto newspaper, challenging claims by a police officer charged with her son’s murder that the boy had been hit by a warning shot.

“He was shot in cold blood — all the eye witnesses say this,” she said.