Thousands of Greeks, furious at the government's austerity measures, gathered outside parliament in the capital Athens, as the second day of a general strike and mass protests began.
The mass action on Thursday comes as Greece's parliament takes a final vote on austerity laws, cutting wages and raising taxes.
Protesters began heading to the capital's main Syntagma Square outside Parliament, while one communist party-backed union vowed to encircle parliament in an attempt to prevent lawmakers from accessing the building for the vote.
On Wednesday, all 154 of the ruling Socialists' deputies voted in favour of the austerity measures, which face further scrutiny and votes on specific articles on Thursday before becoming law.
The implementation of the laws are crucial for the country to receive its next batch of bailout funds and avoid bankruptcy.
On Wednesday, demonstrators hurled stones and firebombs at police in front of the parliament as tens of thousands rallied on the first day of the 48-hour nationwide strike.
Protesters had pushed up to the steps in front of the parliament building itself, setting fire to a sentry box occupied by ceremonial guards at the adjacent Tomb of the Unknown Soldier.
Police responded by firing rounds of tear gas into the crowd to calm the anger that is growing in Athens' Syntagma Square, the plaza next to the parliament which has become a focal point for anti-austerity protests.
More than 7,000 police had been assigned to the city to deal with anticipated trouble with hundreds in riot gear stationed near the parliament building.
'Mother of all strikes'
Al Jazeera's Andrew Simmons, reporting from Athens, said the two-day shutdown was being described as "the mother of all strikes" as it involved every facet of public life.
"Protesters wanted it to be their day, to get their message across: ‘No to more swingeing cuts! No to a whole different life ahead!' Simmons reported.
"But the whole event was high-jacked by a violent minority of no more than 200, who were intent on having a standoff with the police."
Several injuries were reported, mainly from minor burns and cuts to the head. There were also serious clashes away from the scene of the main rally, which attracted more than 100,000 people, according to police estimates.
"The mood was one of anger, with a minority intent on clashing with riot police. But it was also one of utter frustration among those trying to make their voices heard above rounds of tear gas," Simmons said.
Our correspondent said the government was dismissive of further dialogue with unions to discuss alternative ways to promote growth.
"It is instead calling for unity saying there is no other solution but to do what it takes for a second financial bailout," he said.
'Who are they trying to fool?'
Public sector pay cuts, pension cuts and mass layoffs are being demanded by international lenders in exchange for more bailout funds.
The latest strike by Greek workers has shut down government departments, businesses and public services, as well as shops and bakeries, while flights and public transport were cancelled or disrupted.
"Who are they trying to fool? They won't save us. With these measures the poor become poorer and the rich richer. Well I say: 'No, thank you. I don't want your rescue'," said 50-year public sector worker Akis Papadopoulos.
Clashes also marred demonstrations on the island of Crete, where more than 20,000 gathered to protest the bill, and in the cities of Thessaloniki, Volos, Lamia, and Patras, police said.
Wednesday's action comes as European Union leaders scramble to outline a new rescue package in time for a summit on Sunday that hopes to agree measures to protect the region's financial system from a potential Greek debt default.
"We are in an agonising but necessary struggle to avoid the final and harshest point of the crisis," Evangelos Venizelos, Greece's finance minister, told parliament.
"From now and until Sunday were are fighting the battle of all battles."
Trapped in the third year of deep recession and strangled by a public debt amounting to 162 per cent of gross domestic product, which few now believe can be paid back, Greece has sunk deeper into crisis.
Unions had urged deputies not to pass the law. "If they have any humanity, decency, sense of pride and Greek soul left, they must reject the bill," Nikos Kioutsoukis, a top official in private sector union GSEE which is leading the strike with its public sector counterpart ADEDY, said before the vote.
Simmons said "civil servants will have their wages cut by 15 per cent, 30,000 others in the public sector will be suspended on partial pay - 10,000 more than originally planned.
"They will be given 60 per cent of their wages for one year - in the hope that would have found a new employer by year’s end. And all temporary contracts in government will be terminated.
"The first day of strike is holding, and holding firmly."
Source: Al Jazeera and agencies