The Greek parliament has approved a deeply unpopular austerity bill to secure a second bailout from the European Union and International Monetary Fund and avoid a messy default.
Before the parliamentary vote, serious violence broke out on the streets Athens and spread to other Greek towns and cities, including on the holiday islands of Corfu and Crete.
The bill sets out €3.3bn in wage, pension and job cuts for this year alone.
A number of buildings were set alight in Athens in protests against the new austerity plans.
Historic cinemas, cafes and shops went up in flames as Greek riot police struggled to pin down anti-austerity protesters roaming around central Athens.
"Around ten buildings have been set ablaze, most of them using petrol bombs," Nikolaos Tsongas, a spokesman for the fire brigade, told AFP.
Greek police used tear gas on petrol bomb-throwing protesters outside parliament.
Reports claimed some 100,000 protesters had gathered outside the building and at nearby Omonia Square, with some 3,000 police deployed.
Earlier, Finance Minister Evangelos Venizelos said parliament must approve the government-approved plan needed to unlock a €130bn rescue fund from the EU and the IMF or allow Greece to default.
Mr Venizelos said: "The situation is very clear. Tonight at midnight before the markets open the Greek parliament must send the message that our nation can and will (support the debt deal).
"Today we must understand, and persuade Greek citizens, that when you have to choose between bad and worse, you will choose the bad to avoid the worst."
On Saturday, Greek Prime Minister Lucas Papademos told politicians to back a deeply unpopular EU/IMF rescue in a vote today or condemn the country to a "vortex" of recession.
He spoke in a televised address to the nation on the eve of the vote.
The effort to ease Greece's huge debt burden has brought thousands on to the streets in protest, and there were signs yesterday of a small rebellion among MPs uneasy with the extent of the cuts.
Mr Papademos said parliament had a historic responsibility to back the bill, or face catastrophic consequences if Greece misses a 20 March deadline to service its debt.
He said "a disorderly default would set the country on a disastrous adventure," adding that "it would create conditions of uncontrolled economic chaos and social explosion".
"The country would be drawn into a vortex of recession, instability, unemployment and protracted misery and this would sooner or later lead the country out of the euro."
Parliament's finance committee had already approved the bill.
The Papademos coalition has a huge majority, which ensured parliament approved the package needed to secure Greece's second bailout since 2010. But the number of dissenters is growing.
Six members of the Papademos cabinet have already resigned.
In an interview with the newspaper Imerisia, Deputy Finance Minister Filippos Sachinidis described the catastrophe he believes Greece would suffer if it failed to meet debt repayments of €14.5bn due next month.
He said: "Let's just ask ourselves what it would mean for the country to lose its banking system, to be cut off from imports of raw materials, pharmaceuticals, fuel, basic foodstuffs and technology."
On the second day of a 48-hour protest strike, about 50 Communist party activists draped two large banners on the ramparts of the Acropolis, reading: "Down with the dictatorship of the monopolies and the European Union."
Members of the conservative New Democracy party, which has a big lead in opinion polls before elections possible in April, were expected to back the deal solidly. Around ten had threatened not to.
