People walk on the main shopping street in central Athens, Saturday Dec. 20, 2008. There is heavy... 
(AP)
Hundreds of rioters battled police in central Athens on Saturday, fire-bombing a credit reporting agency and attacking the city's Christmas tree two weeks after the police shooting of a teenager set off Greece's worst unrest in decades.
Saturday's violence followed a memorial gathering at 9 p.m. (1900 GMT) where 15-year-old Alexandros Grigoropoulos died Dec. 6, in the Athens neighborhood of Exarchia.
The rioters, using the National Technical University of Athens as a base, launched attacks against police, throwing rocks and petrol bombs and erecting roadblocks.
Security forces are prevented by law from entering the university grounds unless the school administration gives the go-ahead, but so far no permission has been given.
Grigoropoulos' fatal shooting touched a nerve among Greek youth, who took to the streets to protest what they see as random police violence. The protests have been fanned by perceptions of corruption among politicians and poor job prospects as the economy takes a turn for the worse.
Saturday's clashes dashed the hopes of the government and police that protest fatigue would set in as Christmas neared.
Saturday evening, masked men broke into the building housing the offices of Tiresias SA, a company that keeps records of delinquent debtors and cardholders, and firebombed the company's offices. The fire was extinguished but the company's offices were destroyed, witnesses said.
At around 4 p.m. Saturday, about 150 youth attacked the Christmas tree at Syntagma Square in central Athens, hanging trash bags from its branches before clashing with riot police. The square was cleared within two hours. At least three news photographers were injured by police batons. The tree survived the attack.
The original Christmas tree was burned to the ground Dec. 8, during the worst night of rioting.
In Thessaloniki, a group of self-styled anarchists occupied a movie theater in the city's main square and threw cakes and candy at Mayor Vassilis Papageorgopoulos and one of his deputies. The mayor was attending an open-air Christmas event near the theater, distributing the sweets to children with sickle-cell anemia when the rioters disrupted the event. Later, a group emerged from the theater and attacked a Nativity scene, throwing away the Christ figure.
