Athens  - At approximately this time every year, Greeks young and old would normally be seen gathered around a brightly-lit Christmas tree in central Syntagma Square and eagerly shopping for gifts along the highly popular commercial street of Ermou.

But as clashes between students and police continued for a third straight day Monday, with thousands attacking police stations, government buildings, banks and businesses, no one in central Athens appeared to be in the Christmas spirit.

Instead, citezens were clearly running for cover as self-styled anarchists set fire to the citys Christmas village in Syntagma Square, located across from parliament.

Others attempted to bypass bombs, stones, overturned cars and tear gas in a city now resembling a war zone.

Ermou Street, normally a shoppers paradise which is filled with name brand stores was still clouded with smoke on Monday after riots burned several buildings.

Shop windows across Athens have been decorated with lights and the citys mayor was prepared to launch the start of the festive season with music and food when the violence exploded, triggered by the killing of a teenager by police.

More than 150 private businessesin Athens have been seriously damaged by the attacks.

Prime Minister Costas Karamanlis once again appealed for calm after an emergency meeting Monday with his ministers and top security officials, trying to find a way to break the chain of violent events.

"I have asked the Economy Ministry to explore all possibilities so that we can compensate citizens for damage suffered," said Karamanlis in a televised address.

Thousands of students, armed with fire bombs and stones, clashed with police and smashed storefronts in the northern port city of Thessaloniki on Monday while gangs of youths attacked police stations and government buildings in Athens during demonstrations called by student groups and left-wing parties.

As dusk settled upon the Greek capital hooded youths could be seen setting fire to a number of shops, government buildings and party offices along Panepistimiou Avenue, the site of the latest demonstration called by the Greek Communist Party.

Clearly the worst riots Greece has seen in recent years began within hours of the fatal shooting of a teenager on Saturday night in the bohemian district of Exarhia, in central Athens.

Two police officers have been arrested and charged with manslaughter.

From the northern city of Veria and Kavala to the central city of Trikala, students battled riot police who retaliated by firing tear gas. On Crete and the island of Corfu, gangs of high school students threw chairs, wooden objects and rocks at security forces.

More than 50 people have been treated for minor injuries in hospitals across the country and officials said 40 policemen have been hurt in the Greek capital during the riots.

The shooting of the boy hit a raw spot for thousands of Greeks and youngsters, disillusioned by scandals, economic discontent and growing poverty.

Public unrest has grown with the conservative government's austerity measures, with unions regularly demonstrating against privatizations, pension reforms and the cost of living. One-fifth of Greeks live below the poverty line.

"This was bound to happen. The government and police believe they are invincible and that the public should put up with its scandals and brutality," said 45-year-old housewife Angeliki Papadopoulou, summing up a widely-held view.

University professors meanwhile began a three-day walkout on Monday and tens of thousands of students refused anyway to attend classes, in protest. (dpa)