Voting has begun in Greece in the most uncertain and critical parliamentary elections for decades.
The result of the crucial vote could throw the debt-stricken country's future into further doubt and shake the wider eurozone.
After two years of austerity cuts, polls indicate that voters are set to punish Greece's two main parties for having accepted yet more belt-tightening measures in return for two bailouts worth $314bn.
The socialist Panhellenic Socialist Movement or PASOK party and the New Democracy conservatives have alternated in power since the end of a military junta in 1974, but a seismic shift is expected on Sunday, with as many as half of the votes going to around 30 smaller parties.
Al Jazeera's John Psaropolous, reporting from Athens, said: "People are going to the polls to voice their anger at cut pensions, salaries, and increased taxes over the past two years, which have now accumulated and had a collective impact on household finances.
"People are beginning to dip below the poverty lines in greater numbers, more than ever before."
'New political era'
The head of Greece's main left-wing party PASOK, former finance minister Evangelos Venizelos, was booed and heckled as he cast his vote in Sunday's election.
Five or six people on nearby balconies shouted "thief" and another said he was "forced to go to Germany to find work",
said an AFP reporter at the scene.
Antonis Samaras, the leader of the New Democracy party, and Lucas Papademos, the outgoing technocrat prime minister heading the current interim government, also cast their votes early on Sunday.
Papademos said that he expected a new government to be formed "this week" but opinion polls suggesting this might be a tall order.
"We are all agreed that these elections are most crucial. Everyone has to make a decision, not just on who will govern but on what path the country will take in the coming decades."
Speaking to our correspondent Psaropolous, a candidate for one of Greece's smaller centralist parties, Drasi, that has just stood for elections once before, said that Greece was entering a new era of politics. He said he hoped that this will create an avenue for new parties to be represented.
"There are voices that will do justice to a party system where the smaller parties may have a role play in a future goverment," he said.
He said that While austerity measures weigh highest on the agenda, voters are fed up with decades of corruption and cronyism.
Immigration has also been an issue, raising the prospect that the neo-Nazi Golden Dawn party, with a swastika-like emblem and an admiration for Hitler, may enter parliament.
Greece has written off a third of its debts and is in its fifth year running of recession.
One in five workers is unemployed, its banks are in a precarious position, and pensions and salaries have been slashed by up to 40 per cent.
Our correspondent said that the only party running in this election that is unequivocally supporting the bailout measures is the socialist party.
"Everybody else is either campaigning, against the memorandum, in favour of abolition, complete abrogation of abolition of responsibilities, or in favour of a modified renegotiated memorandum," said Psaropolous.
Al Jazeera's reports that almost a third of shops in Athens have closed in the economic downturn.
Both PASOK and New Democracy want the "troika" of the European Union, International Monetary Fund and European Central Bank to be more flexible with Greece in their bailout deals, but for many smaller parties this does not go far enough.
"We need to break from this corrupt political system of lackeys of foreign imperialism," Petros Alachmar, 31, an activist from the far-left Syriza party, told the AFP news agency. "We have had enough of austerity measures."
But with Athens having committed to finding in June another $15bn in savings through 2014, any ambition to renegotiate terms "suggests a degree of liberty they do not have," Swiss bank UBS said in a research note.
New Democracy is expected to win the most votes, but not enough for leader Samaras to govern without partners. One might be PASOK, its current partner in a stop-gap coalition created to pass tough austerity measures through with their combined voting punch.
However, our correspondent said that as this has lost voting power with both of parties, "the conservative leader ... hasn't said that he is going to drop the austerity package, he has said the he is going to try to renegotiate it."
Another possibility might be fresh elections.
If the two parties fail to win a big enough majority to go into a coalition, they will have to persuade groups opposed to the bailout to join them in government, raising fears that Greece could renege on its promises to international lenders and head down a path towards bankruptcy and an exit from the euro.
Al Jazeera's Barnaby Phillips, reporting from Athens on Saturday, said, "As a result of the opinion poll blackout, it is not so easy to predict the votes, but it seems people may be drifting away from traditional parties, and moving towards the extremes on the left and on the right," he said.
Exit polls are expected shortly after voting ends at 16:00 GMT with the first representative official results not expected much before 20:00 GMT.
In comments widely quoted by Greek newspapers on the eve of Sunday's vote, German Finance Minister Wolfgang Schaeuble said that if Greece's new government deviated from its commitments the country would have to "bear the consequences."
|Follow our comprehensive Euro Crisis spotlight coverage
"Membership of the European Union is voluntary," he said.
Holger Schmieding, economist at Germany's Berenberg Bank, said there was a 40 per cent risk of Greece leaving the eurozone this year, with a "high" chance that no stable government willing to implement more reforms can be formed.
With Portugal and Ireland also receiving aid, and Italy and Spain on shaky ground too, last year there were worries of some sort of break-up of the eurozone.
These fears have subsided in recent months but have not completely disappeared.
Germany, in particular, Europe's paymaster-in-chief and the leading proponent of austerity, amid growing calls for more focus on growth, will be watching events in Athens just as much as France's election, also on Sunday.