Riot policemen throw stones towards protesters outside of the main Administrative building of Athens' University, December 8, 2008.

Policemen watch protesters outside of the main Administrative building of Athens' University, December 8, 2008.

]ATHENS, Dec. 8 (Xinhua) -- New clashes broke out on Monday between police and protesters across Greece for a third day, after the death of a 15-year-old boy shot by police on Saturday.

Fires were burnt in the center of Athens and hundreds of people were wandering through the streets, some attacking banks, businesses and vehicles.

A large Christmas tree in central Syntagma Square was set on fire and windows on hotels, government buildings and departments stores were smashed.

Schools and universities in Athens were closed for at least two days.

Hundreds of students rushed to the center of the major cities in Greece and threw petrol bombs and set fires to buildings and vehicles while the police used tear gas against rioters.

Meanwhile in Germany, a dozen demonstrators occupied the Greek consulate in Berlin, replacing the Greek flag with a banner proclaiming Greece a "murderer state." There were also protests at the Greek Embassy in London, according to Athens News Agency.

Greek Prime Minister Costas Karamanlis has called an emergency cabinet meeting Monday night and he will meet President Karolos Papoulias on Tuesday morning to inform him of the situation prevailing in the country.

Local media reported that it is a catastrophe and Athens is in a big chaos.

Earlier on Monday, Karamanlis has gone on television to appeal for calm. He said "extreme elements" were taking advantage of the situation to engage in vandalism and pledged to compensate businesses damaged. Unfortunately, extreme elements have exploited this sad event for their own purposes.

Massive unrest, sparked by the death of a 15-year-old boy Saturday in Athens, was soon expanded to major Greek cities. The two police who were involved in the case have been arrested. A coroner's report shows the boy was shot in the chest.