Greeks voted on Sunday in a referendum that could determine their future in Europe's common currency, with banks shuttered, the treasury empty and a population desperate, angry and so deeply split that the outcome was too close to call.

The referendum is officially a Yes or No vote on a bailout offer from creditors, but a 'Yes' could bring down the government of Prime Minister Alexis Tsipras, while European leaders say a 'No' could force a chaotic exit from the euro.

The country of 11 million people is being asked whether to accept the offer which left-wing leader Tsipras rejected eight days ago. Elected in January on a promise to end years of crippling austerity, he calls the offer a “humiliation”.

He is urging a resounding ‘No’, saying it would give him a strengthened mandate to return to negotiations and demand a better deal, including a writedown on Greece’s massive debt.

His European partners, however, say rejection would set Greece on a path out of the euro, with potentially far-reaching consequences for the global economy and Europe’s grand project of an unbreakable union.

"I voted 'No' to the 'Yes' that our European partners insist I choose," said Eleni Deligainni, 43, in Athens. "I have been jobless for nearly four years and was telling myself to be patient ... but we've had enough deprivation and unemployment."

Angry and exhausted after five years of pension cuts, falling living standards and rising taxes, Greeks now face closed banks, rationed ATM withdrawals and the prospect of the country literally running out of cash.

Pensioners besieging bank gates to claim their retirement benefits, only to leave empty-handed and in tears, have become a symbol of the nation's dramatic fall over the past decade, from the heady days of the 2004 Athens Olympics to the ignominy of bankruptcy and bailout.

Tsipras, a 40-year-old former student activist, has framed the referendum as a matter of national dignity and the future course of Europe.

“As of tomorrow we will have opened a new road for all the peoples of Europe,” he said after voting in Athens, “a road that leads back to the founding values of democracy and solidarity in Europe.”

A ‘No’ vote, he said, “will send a message of determination, not only to stay in Europe but to live with dignity in Europe.”

Not everyone agreed.

“You call this dignity, to stand in line at teller machines for a few euros?” asked pensioner Yannis Kontis, 76, after voting in the capital. “I voted 'Yes' so we can stay with Europe.”

Polls close at 7 pm (1200 EDT), with the first official projection of the result expected at 9 pm.

Most opinion polls have the ‘Yes’ vote narrowly in front. But all have been within the margin of error.

‘CANNOT END LIKE THIS’

Called at eight days’ notice, the referendum offers Greece a ‘Yes’ or ‘No’ vote on a proposal that is no longer on the table, which would have required cuts to pensions and hikes in taxes that Tsipras says would be ruinous.

Given the chaos of the past week, in which Greece became the first developed economy to default on a loan with the International Monetary Fund, creditors say a new deal will have to be drafted, probably involving harsher terms.

Anxious Greeks rallying for a 'Yes' vote say Greece has been handed a raw deal but that the alternative, a collapse of the banks and a return of the old drachma currency, would be far worse.