Tens of thousands of Greeks are taking part in the first general strike of 2013, as workers renew their protest over austerity measures.
Crowds marched towards parliament in Athens, beating drums and blowing whistles as part of the 24-hour strike.
Minor clashes broke out at one stage when police fired tear gas at hooded youths throwing stones.
The strike has been called by Greece's two biggest trade unions, representing half the four million-strong workforce.
"We are protesting about pensions, emergency taxes, the high cost of life," retired factory worker Kyriakos Anastassiadis told the Associated Press.
The strike shut schools and left hospitals with emergency staffing. Domestic flights and long-distance train services were cancelled.
Ilias Iliopoulos, secretary-general of Adedy public sector union, said the strike was an attempt to "get rid of the bailout deal".
"A social explosion is very near," he said.
Demonstrations were also being held in Crete and in the second-largest city of Thessaloniki, where some 17,000 people protested peacefully.
The strikes come days before international lenders are due in the capital to discuss the next instalment of a bailout.
The debt-ridden country is being kept afloat by billions of euros from other eurozone countries and the International Monetary Fund.
In return, the government has imposed waves of unpopular spending cuts and tax rises, hitting pay and pensions and sending unemployment soaring to more than 26%.
Strikes and violent protests have become commonplace.
Greece's coalition government secured the latest tranche of bailout money at the end of last year, and Finance Minister Yannis Stournaras told the BBC the worst was over for his country.
However, the BBC's Mark Lowen in Athens says the strike is a reminder that government confidence in a slowly improving economic situation is not shared by many on the streets.
Our correspondent says the only difference between Wednesday's strike and earlier protests is that public transport has been largely unaffected.
Prime Minister Antonis Samaras's eight-month-old government has taken a tough line on strikers, invoking an emergency law twice in recent months to order seamen and metro staff back to work.
But despite such measures, strikes have recently picked up.
A one-day visit by French President Francois Hollande on Tuesday went largely unreported because Greek journalists were on strike.
Our correspondent says more than 20 general strikes since the crisis erupted have failed to change government policies, and this one is unlikely to be any different.