ATHENS, Greece -- Greek anger over new austerity measures and layoffs erupted into violence outside parliament on Wednesday, as demonstrators threw stones and gasoline bombs and riot police responded with tear gas.
Wednesday was the first day of a two-day general strike that unions described as the largest protests in years. The labor action, which grounded flights, disrupted public transport and shut down shops and schools, comes ahead of a parliamentary vote Thursday on new tax increases and spending cuts.
International creditors have demanded the reforms before they give Greece its next infusion cash. Greece says it will run out of money in a month without the $11 billion bailout money from its partners that use the euro and the International Monetary Fund.
Most of the 100,000 or so protesters that converged in central Athens marched peacefully, but crowds outside of parliament clashed with police who tried to disperse them with tear gas. Some people set fire to a presidential sentry post.
Nearby, groups of protesters tore chunks of marble off building fronts with hammers and crowbars and smashed windows and bank signs. Many of those involved in the violence wore black clothes with hoods, masks or motorcycle helmets. Vendors sold swimming goggles to rioters, who used them to ward off the tear gas.
Thousands of people watched the skirmishes, some standing on kiosk roofs to get a better view. Trash was strewn around the streets, and some protesters set clumps of it on fire.
In Greece's second city of Thessaloniki, protesters smashed the facades of about 10 shops that defied the strike and remained open, as well as five banks and cash machines. Police fired tear gas and threw stun grenades.
All sectors -- from dentists, hospital doctors and lawyers to shop owners, tax office workers, pharmacists, teachers and dock workers -- walked off the job ahead of a parliamentary vote Thursday on new austerity measures which include new taxes and the suspension of tens of thousands of civil servants.
Flights were grounded in the morning but some resumed at noon after air traffic controllers scaled back their strike plan from 48 hours to 12. Dozens of domestic and international flights were still canceled. Ferries remained tied up in port, while public transport workers staged work stoppages but kept buses, trolleys and the Athens metro running to help protesters.
In Parliament, Finance Minister Evangelos Venizelos told lawmakers that Greeks had no choice but to accept the hardship.
"We have to explain to all these indignant people who see their lives changing that what the country is experiencing is not the worst stage of the crisis," he said. "It is an anguished and necessary effort to avoid the ultimate, deepest and harshest level of the crisis. The difference between a difficult situation and a catastrophe is immense."
About 3,000 police deployed in central Athens, shutting down two metro stations near parliament as protest marches began. Protesters banged drums and chanted slogans against the government and Greece's international creditors who have pressured the country to push through rounds of tax hikes and spending cuts.
"We just can't take it any more. There is desperation, anger and bitterness," said Nikos Anastasopoulos, head of a workers' union for an Athens municipality.
Other municipal workers said they had no option but to take to the streets.
"We can't make ends meet for our families," said protester Eleni Voulieri. "We've lost our salaries, we've lost everything and we're in danger of losing our jobs."
Demonstrations during a similar 48-hour strike in June left the center of Athens convulsed by violence as rioters clashed with police on both days while deputies voted on another austerity package inside Parliament.
Piles of garbage festered on Athens street corners despite Tuesday's government order to garbage crews to end their 17-day strike. Earlier in the week, private crews removed some trash from along the planned demonstration routes, but mounds remained on side streets, along some of the march routes and in city neighborhoods.
Protesting civil servants have also staged rounds of sit-ins at government buildings, with some, including the Finance Ministry, under occupation for days.
Prime Minister George Papandreou appealed Tuesday for the protests to end.
"I would like to ask all those who occupy ministry buildings, choke the streets with garbage, close off ports, close off the Acropolis, if this helps us stand on our feet again -- of course it does not," Papandreou told parliament.
Most stores in the city center, including bakeries and kiosks were shut Wednesday. Several shop owners said they had received threats that their stores would be smashed if they attempted to open.
The measures to be voted on Thursday come after more than a year and a half of repeated spending cuts and tax increases. They include new tax hikes, further pension and salary cuts, the suspension on reduced pay of 30,000 public servants and the suspension of collective labor contracts.
A communist party-backed union has vowed to encircle Parliament Thursday in an attempt to prevent deputies from entering the building for the vote.
The reforms have been so unpopular that even some lawmakers from the governing Socialists have indicated they might vote against them.
Meanwhile, European countries are trying to work out a broad solution to the continent's deepening debt crisis, ahead of a weekend summit in Brussels. It became clear earlier this year that the initial bailout for Greece was not working as well as had been hoped, and European leaders agreed on a second, $151 billion bailout. But key details of that rescue fund, including the participation of the private sector, remain to be worked out.