Strikes hit schools and hospitals and brought public transport in Athens to a halt on Friday in protests against austerity measures imposed by the Greek government.
Police fired teargas to disperse a group of youths throwing stones at riot police and scuffling with other protestors.
Pressured by financial markets and the European Union, Greece announced on Wednesday 4.8 billion euros ($6.5 billion) in new spending cuts and tax hikes to tackle its huge fiscal deficit and 300 billion euro ($408 billion) debt pile.
On Friday, the only buses on the streets belonged to the riot police. At the airport, more than 60 flights were canceled as unions called impromptu work stoppages and protesters shouting "never, never, never" marched on parliament.
Pagiaslis Giannis, 57, a private sector employee taking part in one of the marches, said the protests were a healthy response and that while people wanted to express their anger they also understood that belt-tightening was necessary.
"It's like the slap that a father gives to his child and the child reacts even though he knows he was in the wrong," he said.
The protests escalated as an opinion poll showed strong opposition to some measures such as higher VAT and a freeze on public pensions but support for moves to raise tax on alcohol, cigarettes and luxury goods.
The survey also showed that 78 percent of people believed there was a high probability that all of the government's measures would be implemented.
Ratings agencies and other EU governments have said delivery will be key in determining whether Greece can re-establish its credibility on the world stage and as a borrower.
Figures published on Friday showed that foreign investors bought 77 percent of a 5 billion euro bond sold by the Greek government this week with the biggest demand coming from Britain and Germany.
Friday's survey did not ask how the crisis was being handled overall but two polls in late February before the latest round of cuts showed most Greeks thought the government was dealing with it effectively.
The latest protests took place as Greek Prime Minister George Papandreou traveled to Germany for a meeting with Chancellor Angela Merkel in the hope of persuading her to back more concrete EU support measures for Greece.
Papandreou has said it is time for the European Union to do its bit although Germany again moved to temper his expectations with Economy Minister Rainer Bruederle saying his government "does not intend to give a cent" to Greece.
Opposition to cutbacks has so far been relatively muted for a country with a tradition of street protest. Police officials on Friday estimated about 12,000 demonstrators were on the streets.
Those polled in the latest survey did not expect the government to get an easy ride, however, with 62 percent predicting social unrest was highly likely in the next year.
"Something must be done to avoid bankruptcy but I believe that strikes will continue for months," said Dimitris Thanos, a kiosk employee in the center of Athens.
Meanwhile the main public sector union ADEDY brought forward a planned national strike to March 11 from March 16 and its sister private sector union GSEE said it would join them. The two unions represent half Greece's 5-million workforce.
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