Greece votes in parliamentary elections
Greeks are voting in parliamentary polls, with the country's two mainstream parties expected to lose support to anti-austerity candidates.
The centre-left Pasok and centre-right New Democracy parties have been in coalition since last November.
They are both expected to suffer due to opposition to the austerity measures imposed by the government in exchange for international bailout funds.
No single party is expected to gain a majority.
The ability of any new government to carry on with the austerity programme will be crucial for Greece's continued access to bailout funds from the EU, the European Central Bank and the International Monetary Fund - the so-called Troika.
Any political instability may prompt fresh questions over the country's place in the eurozone.
If any new Greek government deviated from its fiscal commitments the country would have to "bear the consequences," German Finance Minister Wolfgang Schauble said.
Under the current plan, a further 11bn euros of savings in spending are due to be found in June.
Casting his vote, Prime Minister Lucas Papademos said the election would determine the "course that the country will take for the coming decades".
Many Greeks hope pressure from the EU may be relaxed in the event of a victory for French socialist presidential candidate Francois Hollande, who has voiced scepticism over austerity, the BBC's Mark Lowen reports from Athens. France is also holding elections on Sunday.
Pasok and New Democracy have dominated Greek politics since the 1970s, but many voters are disillusioned with their handling of the crisis and angry over perceived corruption, our correspondent reports.
A range of smaller parties looks set to benefit, from the communists to the anti-immigrant, far-right Golden Dawn party, he adds.
"I am going to vote one of the small parties. I have had enough of ND and Pasok," one voter, psychology student Maria, told the AFP news agency. "Ever since I was born people have just voted for them."
Some polls indicate that Golden Dawn could gain more than 5% of the vote and enter parliament for the first time.
In his party's closing rally on Friday, Pasok leader Evangelos Venizelos said Greeks faced a choice between continuing with the austerity programme in order to stay in the eurozone and "mass poverty".
New Democracy's leader Antonis Samaras said the Left was "playing games with the country's European future".
New Democracy is expected to emerge from the poll as the largest party, but with only around 22% of the vote.
Pasok, which has been governing in coalition with New Democracy since last November, has been in second place in opinion polls with around 18%.
Left-wing parties opposed to the terms of the bailout deal have collectively scored around 30% in opinion polls.