Thousands of people protested across Greece on Thursday against the next round of spending cuts, required in return for another bailout installment.
The 24-hour strike is the country's 20th national stoppage since the debt crisis erupted two years ago and comes as EU leaders met in Brussels.
Taxi drivers, doctors, teachers and air traffic controllers were among those taking part in the rallies.
Athens police used tear gas to disperse demonstrators throwing petrol bombs.
Syntagma Square was temporarily shut down but has since reopened to traffic; it was quite a small protest as Greek protests go and remained mainly peaceful,
Protesters threw petrol bombs and stones at police blocking off parts of the capital's main square before parliament. Officers responded with tear gas and stun grenades.
A 65-year-old man suffered a fatal heart attack during the demonstration, which was said not to be linked to the protests.
But local media are reporting that he was tear-gassed, RT's correspondent says.
Thousands of protesters gathered for rallies ahead of two separate demonstrations in central Athens, amid a heavy police presence.
Other protests were also planned across the country.
The strike takes place as European leaders are meeting in Brussels for a summit in which Greece's economic fate is likely to feature large.
Greece is currently preparing a 13.5bn-euro (£11bn; $17.7bn) austerity package to satisfy the "troika" of International Monetary Fund, European Commission and European Central Bank lenders in return for its next 31.5bn-euro tranche of aid.
The country is due to run out of money next month.
Trade union leaders say they hope to show EU leaders that a new wave of wage and pension cuts will only worsen the plight of the Greek people.
Greece is in its fifth consecutive year of recession and more than a quarter of its workforce is unemployed.
"Just once, the government ought to reject the troika's absurd demands," said Yannis Panagopoulos, head of the GSEE private sector union.
"Agreeing to catastrophic measures means driving society to despair, and the consequences as well as the protests will then be indefinite," he added.
The BBC's Mark Lowen in Athens says cracks are already appearing within the coalition government as party leaders disagree over job losses and other austerity measures.
Anger has led to a loss of faith in the state, he says, with Greeks increasingly turning to political extremes such as the neo-Nazi Golden Dawn party.
Although the Greek government has vowed to stay the course, social unrest could yet prove explosive, our correspondent adds.