Shots were fired at an anti-riot van in Athens on Tuesday and youths damaged a police car as some 2000 students marched in new protests that have rocked the capital since police killed a teenager.

At the start of the march, roughly a dozen youths toppled a police vehicle, with the officers inside escaping unscathed.

Earlier in the day, shots were fired at a riot police van in the Goudi district of Athens, missing the 23 police on board but hitting the engine. One of the van's tyres also burst.

The police found two bullet remains from a 7.62 calibre rifle apparently fired from inside a park that forms part of the Athens university campus.

Youths have targeted police stations and torched police vehicles in three weeks of sporadic unrest over the death of 15-year-old Alexis Grigoropoulos.

Around 2000 university and high school students peacefully marched on parliament, shouting slogans against the police and the conservative government which is clinging to power by a one-seat majority in parliament.

"This bullet did not come by accident, the government, the cops and the state are guilty, (Prime Minister Costas) Karamanlis, you fascist, you can't stop us," the protesters said of the teenager's killing.

Upon reaching parliament, a group of demonstrators set fire to a large paper pig's head sporting a policeman's cap and dumped it at the feet of riot police.

Meanwhile, a group of high-school students staged a separate rally in front of the education ministry slated to be their last before the holidays.

The students — who are expected to decide in early January whether or not to pursue their protests over the teenager's death — claim they continue to occupy about 700 schools and several universities in Greece. The education ministry claims only about 100 are occupied.

The worst rampage Greece has seen in decades

Grigoropoulos was fatally shot on 6 December by a police officer who claims he fired into the air whilst under attack by a group of youths.

The boy's death unleashed a wave of youth anger which initially degenerated into the worst rampage Greece has seen in decades with hundreds of stores in several cities vandalised and looted in the days following his death.

The violence has since largely subsided, allowing Athenians to salvage a narrowed-down Christmas shopping season.

But skirmishes with young protesters continue around occupied university buildings which are off-limits to police under education laws dating from the restoration of democracy from the seven-year army junta in 1974.

Karamanlis's government was already in trouble from unpopular reforms and corruption scandals but he has vowed to stay on to help the country steer through the global financial slowdown.

The depth of anti-government sentiment witnessed over the past fortnight has also cost the government dearly in opinion polls.

Socialist leader George Papandreou has overtaken Karamanlis for the first time as the preferred choice for prime minister, and a new survey by pollsters GPO on Monday said the socialists would sweep an election by a massive 22.4-percentage point margin over the ruling party.

AFP