THESSALONIKI, Greece (AP) - Clashes broke out Tuesday at a police station outside Greece's second-largest city of Thessaloniki as residents of a nearby Roma settlement protested the police shooting of a teenage driver during a chase over an unpaid gas station bill.

Protesters smashed a riot police bus and set fire to tires and an excavator vehicle on a nearby road, while riot police responded with volleys of tear gas. Shots could be heard, and police asked journalists in the area to move farther, saying protesters were firing from shotguns.

The clashes came after a 34-year-old police officer appeared in court over the shooting early Monday of a 16-year-old Roma youth who allegedly drove off from a gas station without paying the bill.

The teen, whose identity has not been officially released but was identified by relatives as a member of the Roma community, was hit in the head and hospitalized in critical condition in Thessaloniki.

Before the incident, demonstrations already were planned Tuesday to mark the anniversary of the 2008 fatal police shooting of a teenager in Athens that sparked Greece's worst riots in decades. These annual commemorations often turn violent.

About 6,000 people marched Tuesday night in Thessaloniki to remember the 2008 shooting, and after the protest was over some set fire to trash cans and threw Molotov cocktails at police - who responded with a water cannon and tear gas. No injuries or major damage to property were reported. Police said 16 suspected rioters were detained.

Similar rioting occurred in Athens after the end of the anniversary march in which an estimated 5,000 people took part. Police detained 19 people.

The police officer who appeared in court Tuesday on a felony charge of attempted manslaughter with possible intent and a misdemeanor count of illegally firing his weapon has been suspended.

He said he opened fire because the pickup truck the teenager was driving tried to ram one of the pursuing police motorcycles. The police officer told the prosecutor he had fired “because the lives of my colleagues were in danger.”

He was given until Friday to prepare his defense before appearing before an investigating magistrate.

During the preliminary hearing, scuffles broke out outside the courthouse between police and protesters who held up a banner reading: “It wasn't the gas, it wasn't the money, the cops shot because he was Roma.” Protesters threw rocks and other objects at police, who responded with tear gas.

Some protesters set dumpsters on fire, while others attempted to put out the smoldering trash with water bottles.

Elsewhere in Greece, groups of Roma briefly blocking off major highways at two points in the country's south. State ERT TV said in one case, protesters threw stones at passing motorists and lit fires, forcing police to temporarily stop traffic.

The 16-year-old's shooting occurred outside Thessaloniki at around 1 a.m. Monday. Officers from a motorcycle patrol chased the teenager's pickup truck after a gas station employee reported an allegedly unpaid bill of 20 euros ($21).

In a statement Monday, police said the driver ignored orders to stop and repeatedly ran red lights. The police statement said the driver attempted to ram one of the police motorcycles, “placing the lives of the police officers in immediate danger.” It said two shots were fired in an attempt to stop the vehicle.

Panagiotis Ramos, who was protesting outside the courthouse and identified himself as a family friend of the wounded teenager, dismissed the police version.

“It was a racist shot. It wasn't one, but two,” Ramos said. “The shot was straight. He was trying to finish him off.”

On Monday night, about 1,500 people took part in a protest march organized by left-wing and anarchist groups in central Thessaloniki. Some smashed shops and threw Molotov cocktails at police, who detained six people.

Several hundred people also took part in a mostly peaceful demonstration Monday in central Athens over the teen's shooting as well as a past incident in which a Roma man also was shot during a police chase.

Members of the Roma community in Greece and human rights activists frequently accuse Greek authorities of discriminating against Roma. Several Roma men have been fatally shot or injured in recent years during confrontations with police while allegedly seeking to evade arrest for breaches of the law.

Vassilis Kommatas in Thessaloniki contributed to this report.