Enlarge By Thanassis Stavrakis, AP Protesters throw stones at riot police during clashes in Athens. ATHENS (AP)  Rioters rampaged through Athens and the northern city of Thessaloniki Sunday, hurling Molotov cocktails, burning stores and blocking city streets with flaming barricades after protests against the fatal police shooting of a teenager erupted into chaos. Youths wearing hoods smashed storefronts and cars in Athens. Riot police responded with tear gas while the fire department rushed to extinguish blazes. Several bank branches, stores and at least one building were on fire on a major street leading to the capital's police headquarters. Clashes also broke out near Parliament. Streets quickly emptied as word of the violence spread. Local media reported several people sought treatment for breathing problems. Violence often breaks out during demonstrations in Greece between riot police and anarchists, who attack banks, high-end shops, diplomatic vehicles and foreign car dealerships in late-night fire-bombings that rarely cause injuries. Some believe the anarchist movement has its roots in the resistance to the military dictatorship that ruled Greece from 1967-74. The anarchists often take refuge inside university buildings or campuses, where police are barred under Greek law. The shooting of the 16-year-old boy that set off the first riots took place Saturday night in Exarchia, a downtown Athens district of bars, music clubs and restaurants that is seen as the anarchists' home base. The circumstances surrounding the shooting were initially unclear. Police said the two officers involved claimed they were attacked by a group of youths, and that three gunshots and a stun grenade were fired in response. Youths burning shops, set up flaming barricades and torched cars in cities around the country overnight. At dawn crews cleaned up streets littered with the burned debris of businesses and cars. Tear gas hung in the air. Sunday's riots broke out during demonstrations moving toward the police headquarters in Thessaloniki and Athens. Protesters in the northern city attacked City Hall, two police precincts, several shops and a bank, as well as vans and cars belonging to several Greek television channels. In Athens, violence broke out as more than two thousand protesters marched to the police headquarters. Youths fought with riot police for about two hours before groups split off into different parts of the city. More violence was reported in Exarchia. Interior Minister Prokopis Pavlopoulos promised there would be a thorough investigation into the teenager's death and pledged to punish anyone found responsible. "It is inconceivable for there not to be punishment when a person loses their life, particularly when it is a child," Pavlopoulos said. "The taking of life is something that is not excusable in a democracy." He and Deputy Minister Panagiotis Chinofotis submitted their resignations, which were not accepted by the prime minister. The two officers involved in the shooting have been suspended pending the outcome of the investigation, as has the police chief in the Exarchia precinct. Police said the Saturday night riots left 24 policemen injured, with one remaining hospitalized Sunday morning. Rioters damaged or burned 31 stores, nine bank branches and 25 cars, including six police cars, police said in a statement. Six people were arrested, five of them for theft from damaged stores and one for carrying a weapon, it said. Full details for damage from Sunday afternoon's riots were not immediately available. Copyright 2008 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more