Greek lawmakers backed a stinging new austerity plan demanded by international creditors Wednesday, enraging protesters fighting street battles with police firing tear gas.
Lawmakers voted 155 to 138 for the hotly-disputed package to slash 28.4 billion euros ($40 billion) from the balance of government spending by 2015, a plan aimed at unlocking emergency finance from the EU and the IMF.
An estimated 1,000 hardcore youths hurled missiles at police, who responded with volleys of tear gas that blanketed Syntagma Square in front of the parliament and reached high floors in surrounding buildings.
Security forces drove protesters further away from the parliament, but a blaze broke out at the finance ministry on the far side of the square amid early evening running battles. Firefighters said they could not get at the fire because of the violence.
"We're going to carry on the protest until the government falls, and it will fall," said student Thanas, 22, told AFP.
"It's chaos here, we'll stay whatever happens though, we're going to fight to take back the square," added 22-year-old law student Debbi.
European Union leaders starting with German Chancellor Angela Merkel hailed the result, despite the fact a second vote on the detail behind the measures has still to be held on Thursday.
The euro firmed and Greek stocks again rose as EU president Herman Van Rompuy applauded a "vote of national responsibility."
The yes vote was "the only way to buy time and start the great changes this country needs," Papandreou said, pledging to do "everything to avoid the collapse of this country," with the plans deemed essential to prevent default on its 350-billion-euro debt mountain.
The plan is a condition for 12 billion euros of emergency loans needed by mid-July from stressed eurozone partners and the International Monetary Fund, that could now be unlocked by eurozone finance ministers as early as their next meeting on Sunday.
Eurozone chief Jean-Claude Juncker urged another yes vote on Thursday "in these grave and crucial times for Greece" as MPs started their debate on the "implementation" of radical reforms.
Five lawmakers voted 'present' -- a political statement indicating they could back the second vote if the majority gets squeezed.
"We have taken a big step," Finance Minister Evangelos Venizelos told the Athens News Agency. "Tomorrow we will take the second so that I can go on Sunday to see my Eurogroup partners with real proof of the country's credibility."
Papandreou's only rebel was blind MP Panayotis Kouroublis, who earned an immediate expulsion.
Privatising a dozen utilities and other public assets is aimed at raising 50 billion euros by 2015, but the sale of the state's majority holding in the national electricity company is one particularly divisive element in the detail.
Police said 72 people, including 26 officers, had received hospital treatment, and emergency services said the nearby King George hotel was closed "as a precaution."
Protesters erected makeshift barriers on the square, variously hurling firecrackers, rocks and metal barriers at security forces, before more tear gas sent them scuttling down metro steps, those without masks struggling to breathe or see.
"Everyone in the streets at the moment is really angry, and some are scared, you don't know what's going to happen" joiner John Papadopis, 35, told AFP on the square.
On the second day of a 48-hour general strike, many protesters had said they expected the cocktail of taxes, spending cuts and sell-offs deemed essential for wider eurozone stability to pass -- but that they would be back.
"Too many of these protesters are just out for fun," nearby barmaid Helene told AFP. "They don't have jobs so they come here at night for a party."
The general strike brought about power cuts and ground transport in the capital to a halt.
Once the July cashflow needs are met, a second bailout expected to be worth a similar amount to last year's 110-billion-euro rescue can be thrashed out.
The main sticking point involves how much banks and other private creditors will contribute by way of a 'rollover' of existing debts.