Civil unrest broke out across Greece on Sunday as hundreds of demonstrators clashed with riot police in Athens and the northern port city of Thessaloniki in a second day of protests following the death of a teenaged boy shot by police a day earlier, DPA reported. Both cities resembled war zones as rioters rampaged, setting barricades on fire, along with dozens of cars, stores and banks and at least one apartment building. Despite charges of manslaughter being filed against two of the policemen allegedly involved in the shooting incident, the violence continued unabated. Entire streets and avenues remained blocked by burned and overturned vehicles and garbage bins. Tear gas filled the air along the central Alexandras Avenue in Athens in a second day of protests. Fire brigades rushed to extinguish the flames, including a fire at the Environment Ministry, while hospital attendants could be seen rushing the injured and those suffering from breathing problems to hospital. Hundreds of students taking part in the riots have sought shelter in the Polytechnic and Economic Universities, which is off limits to police under Greek law, reports said. The Polytechnic university was the scene of a major student uprising during the military dictatorship that ruled Greece from 1967- 74. Prime Minister Costas Karamanlis, whose government has been under pressure recently following a spate of scandals, promised a full investigation into events leading to the boy's death. But with violence in full force across the country he called an emergency meeting of interior and public order ministers late on Sunday in an effort to find a solution. The rioting and protests began in Athens late on Saturday, shortly after the shooting in the central district of Exarchia. The exact circumstances surrounding the shooting of a teenage boy - whose age was variously reported as 15 or 16 by media - by police are still unclear. Police said the initial incident started when groups of youths began attacking a police car with stones and firebombs. A warning shot fired by a police officer seriously wounded a teenager in the stomach. The teenager died upon arrival at the hospital.