Tens of thousands of Greeks took to the streets of Athens as part of a nationwide strike against austerity that confined ferries to ports, shut schools and left hospitals with only emergency staff.
Beating drums, blowing whistles and chanting "Robbers, robbers!" more than 60,000 people angry at wage cuts and tax rises marched to parliament.
This was the biggest protest for months over austerity policies required by international lenders.
In the capital, riot police fired tear gas at hooded youths hurling rocks and bottles during a demonstration, mostly of students and pensioners, which ended peacefully.
The two biggest labour unions brought much of crisis-hit Greece to a standstill.
The 24-hour protest strike is against policies which they say deepen the hardship of people struggling through the country's worst peacetime downturn.
Representing 2.5m workers, the unions have gone on strike repeatedly since a debt crisis erupted in late 2009.
The unions are testing the government's will to impose the painful conditions of an international bailout in the face of growing public anger.
The eight-month-old coalition of Prime Minister Antonis Samaras has been eager to show it will implement reforms promised to the European Union and International Monetary Fund.
The IMF and EU have bailed Athens out twice with over €200bn.
The government has cracked down on striking workers, invoking emergency laws twice this year.
Seamen and subway workers have been forced back to work after week-long walkouts that paralysed public transport in Athens and led to food shortages on islands.
Demonstrations were also held in Greece's second-biggest city, Thessaloniki, and on the island of Crete where dozens of protesters hit the streets waving black flags.
In Athens, crowds began to disperse from Syntagma Square outside parliament, but minor clashes between riot police and hooded youths moved to sidestreets.
Labour unrest has picked up in recent weeks.
A visit by French President Francois Hollande in Athens yesterday went largely unreported because Greek journalists were on strike.
Anger at politicians and the wealthy elite has been boiling during the crisis.
Many accuse the government of making deep cuts to wages and pensions while doing too little to spread the burden or go after rich tax evaders.
In a sign it may be buckling under pressure, the government announced on Monday it would not fire almost 1,900 civil servants earmarked for possible dismissal.
The move was despite promising foreign lenders it would seek to cut the public payroll.
Greece secured bailout funds in December, ending months of uncertainty over the country's future in the eurozone.
Analysts have said this had created expectations among Greeks that things would improve for them personally.
Six years of recession and three of austerity have tripled the rate of unemployment to 27%.
More than 60% of young workers are jobless.
Most business and public sector activity came to a halt with schoolteachers, train drivers and doctors among those joining the strike.
Banks pulled down their shutters and ships stayed docked as seamen defied government orders to return to work.