More than 10,000 demonstrators yelling, "Down with the pigs," and carrying black flags marched through a city landscape of burned and looted shops in Athens in a nationwide strike which quickly turned violent as threw fire bombs and chunks of marble at the police.

The 24-hour general strike, called by the country's two largest private and public sector unions, was held amid increasing tensions in the country after days and nights of violence triggered by police shooting dead a 15-year-old youth last Saturday in the bohemian Athens district of Exarchia.

Witnesses said the police officer deliberately aimed for the boy, but a ballistics report, not yet made public, showed on Wednesday the boy was killed by an accidental ricochet.

Despite pleas from the officers of their innocence, clashes erupted at the main court house before the hearing for the two officers accused of the shooting.

Protesters hurled two petrol bombs outside the Athens court as the two officers went before a magistrate for questioning, police said.

The two police, who are both under arrest, were making their first appearance before an investigating magistrate since the fatal shooting of 15-year-old Alexis Grigoropoulos on Saturday.

The petrol bombs were thrown as the lawyer for the police officers, Alexis Kouyias, was preparing to talk to reporters outside the court. The lawyer was not hurt.

Police said the youths who threw the bombs were friends of the dead boy.

The shooting sparked five days of violence across the country already discontented with the government over rising unemployment, scandals and poverty.

Hundreds of youths hurled fire bombs, bottles and stones at riot police on guard in front of parliament, who retaliated with tear gas. The clashes continued for several hours throughout the city centre.

National strike adds insult to injury

After the march, a violent demonstration broke out

The nationwide strike grounded all flights at Athens' international airport, shut down banks and schools and paralysed bus, tram and metro services. Hospitals were operating on emergency staff.

Prime Minister Costas Karamanlis had asked opposition party leaders to unite in an effort to end the crisis and appealed to unions to cancel Wednesday's rally. But no one was willing to compromise.

Instead, the main opposition Socialist party said the government, which has a one-seat majority in parliament, should resign saying it has lost the trust of the people.

Greece's private-sector GSEE and public-sector ADEDY unions are protesting the government's recent pension reforms, which raise the retirement age and cut back benefits.

The unions also oppose recent labour reforms, privatizations and tax-raising measures. The two unions represent more than half of the country's workforce of 5 million.

Rioting eroding patience of Athens citizens

The riots are having a clear effect on the people of Greece

Four successive nights of rioting and looting have left hundreds of cars, stores and buildings charred and gutted at least 10 cities across Greece and left many Athenians angry about the response of the government and police and their inability to stop the destruction.

The protests also spread abroad as the Greek embassies in London, Berlin, Paris and in Cyprus were occupied by demonstrators in the past few days.

Reports said rioters have damaged or destroyed more than 350 stores and 200 banks in Athens, while 50 buildings were damaged by fires. Another 100 stores were damaged in Thessaloniki. Damage is estimated in the millions of euros.

In the centre of Athens the majority of shops were shut for the day while in the popular areas of Plaka and Monastiraki they were devoid of tourists.

Embattled government promises help in recovery

Businesses have been hit by riots and face huge losses

The government, which has seen its ratings fall sharply behind the main opposition Socialists, has promised to compensate businesses for the damage suffered.

The prime minister had made similar promises when large parts of mainland Peloponnese suffered devastating forest fires more than a year ago. Residents in those areas hit by the devastating fires claim the government's promises were never met.

The shooting of the teenager was seen as the last straw by many young Greeks whose economic future is bleak in a country with a high unemployment rate and low wages.

Unemployment is pegged at over 7 per cent, and nearly 20 per cent of Greeks live below the poverty line, earning less than 600 euros ($775) a month.

"Everyone appears to have let our children down. Students have become more hostile towards us and to figures of authority," Christos Kittas said on resigning as the dean of Athens University after rioting spread to campuses.