ATHENS, Greece - A Greek court ordered Wednesday that two policemen be held in jail pending their trial for a teenage boy's fatal shooting -- a death that has sparked five days of intensive riots in cities across the country.

One officer has been charged with murder for allegedly shooting dead 15-year-old Alexandros Grigoropoulos in a confrontation Saturday in Athens. The other officer has been charged as an accomplice to murder. No trial date has been set.

Earlier in the day, protesters attacked Athens' main courthouse with firebombs during a hearing for the two officers. Riot police responded by firing tear gas, and at least two people were injured.

Police whisked the two officers out of a side entrance at the court and drove off in a convoy.

Riot police and youths also clashed in downtown Athens during a demonstration by more than 10,000 people against the government's economic policies.

Greece's two largest labour unions organized the protest, along with a national strike Wednesday that shut down schools, public services, hospitals and flights, increasing the pressure on Prime Minister Costas Karamanlis' fragile conservative government.

The demonstrations and the strike had been scheduled before the riots broke out, but they were fuelled by anger at the government's handling of the riots.

The policemen's lawyer, Alexis Cougias, told reporters that a ballistics examination showed that the teen was killed by a ricochet and not a direct shot. One officer said he had fired warning shots and did not shoot directly at the boy.

"Because he fired in the air to save his life, as a result of this accident ... he faces family and personal ruin," Cougias said.

He said he had been told about the ballistics report by authorities. There was no comment from prosecutors, who do not make public statements on pending cases.

Karamanlis' government has faced growing opposition to changes in the country's pension system, privatization and the loosening of state control over higher education, which many students oppose because they feel it will undermine their degrees.

Support for the government has sunk as gangs of youths marauded through cities since Saturday, torching businesses, looting shops and placing burning barricades across streets.

The clashes in Athens escalated Wednesday into running battles through the city centre, with masked youths pelting police with rocks, bottles and marble blocks from the Athens metro station. The youths shattered windows newly replaced after four nights of rioting.

"The government wanted us to postpone this protest, but they are the ones who have to do something to stop this violence and to improve the quality of our lives," said protester Kalypso Synenoglou, a drama student.

High-school students chanting "Cops! Pigs! Murderers!" and cheered each time a riot policeman was hit by a rock. At least one person was hurt.

Clashes also broke out during demonstrations in the northern cities of Thessaloniki and Kavala.

Storeowners have accused authorities of leaving their businesses unprotected as rioters smashed and burned their way through popular shopping districts.

Karamanlis, however, has ignored calls for him to resign and call early elections.

An opinion poll for the conservative daily Kathimerini published Wednesday found 68 per cent of Greeks believe the government mishandled the crisis -- including nearly half of those who voted for Karamanlis' party last year. Only 18 per cent approved.

The Public Issues survey was based on a sample of 478 people questioned Monday and Tuesday and had a 4.5 per cent margin of error.

Amnesty International has accused Greek police of heavy-handed tactics against protesters, saying police "engaged in punitive violence against peaceful demonstrators" instead of focusing on rioters.

In Ottawa, Foreign Affairs Minister Lawrence Cannon said Canada was saddened by the violence.

"It is our deepest hope that calm and order are restored quickly, " he said in a statement.

He said his department was in constant touch with the Canadian Embassy in Athens, which is monitoring the situation closely.

So far, there have been no reports of any Canadians affected by the violence, the minister added.

-- With files from The Canadian Press.