Hundreds of buildings have been torched and dozens of people have been injured in three days of riots sparked by the death of 15-year-old Alexandros Grigoropoulos. Scores of arrests have been reported, but police fear there could be further unrest when the funeral takes place in an Athens suburb at 1500 (1300 GMT). Schools are shut for the funeral and leaders are holding crisis meetings.

Greek Prime Minister Costas Karamanlis has held talks with President Karolos Papoulias and is also due to meet opposition leaders in an attempt to reach a consensus on what action to take. After an emergency cabinet meeting on Monday, Interior Minister Prokopis Pavlopoulos said the government would not put up with the violence.

But appeals for calm have so far been largely ignored by the mostly young protesters, and plans as to how the violence should be contained remain unclear.

The prime minister vowed on Tuesday morning there would be no leniency in dealing with the rioters. Earlier, he said his government was obliged to protect the community while calling for a sense of solidarity with the Grigoropoulos family. "The unacceptable and dangerous events that have gone on under the most extreme of emotions cannot and must not be tolerated," he said.

However, police appear to be powerless to prevent rioters from attacking symbols of wealth and prestige in Athens, the BBC's Malcolm Brabant reports. A clean-up was under way after protesters wielding petrol bombs set fire to banks, shops, hotels vehicles, rubbish bins and even the city's giant Christmas tree in central Syntagma Square. "Rage is what I feel for what has happened, rage," said a student taking part in the protests. "This cop who did it must see what is to kill a kid and to destroy a life."

Violent clashes have been reported in towns and cities across the country, spreading to Rhodes and Crete on Monday. Police stations were attacked in Piraeus and Corfu. Hundreds of students clashed with riot police in Thessaloniki, Greece's second biggest city, where students used university buildings to stockpile petrol bombs.