More than 60% of Greeks have voted 'No' in a crucial bailout referendum that could ultimately decide whether the country leaves the eurozone, says an official poll.

With more than half of ballot papers counted, 61% rejected EU demands for further austerity, compared with 39% for the Yes campaign.

Celebrations are taking place in Syntagma Square in Athens with flags flying and crowds cheering the news.

"The party is just beginning and is likely to go on for some time," said Sky (Other OTC: BSYBF - news) 's Economics Editor Ed Conway, in the square.

One woman told him the result proves Greek people "are not slaves" and "we are free".

Sky's Europe Correspondent Robert Nisbet said it was a "convincing win" for Greek Prime Minister Alexis Tsipras.

A spokesman for Mr Tsipras said it would allow him to push for a better bailout package from Greece's creditors - the European Union, International Monetary Fund and European Central Bank.

"With this result, the prime minister has a clear mandate from the Greek people," he said. "Initiatives will intensify from this evening onward so that there can be a deal."

Interior Minister Nikos Voutsis said turnout was over 50% and voting took place with "only a minor amount of problematic behaviour".

Defence Minister Panos Kammenos tweeted that the Greeks "proved they don't bow to blackmail, to threats".

EU leaders have previously warned a No vote could push Greece out of the euro - forcing a return of its drachma currency.

Mr Tsipras spoke with French President Francois Hollande on the phone as 'No' campaigners celebrated their victory.

German Chancellor Angela Merkel is due to fly to Paris tomorrow for urgent talks with Mr Hollande.

"The talks with the French president from 6.30pm and over dinner will be about a common assessment of the situation after the Greek referendum and the continuation of the close German-French cooperation on this subject," said a spokesman for Mrs Merkel.

Senior German conservative Michael Fuchs said Mr Tsipras had caused a "disaster" and Europe "must see how to pick up the pieces".

Mr Tsipras had indicated he would step down if the Greek people voted Yes - showing they are in favour of budget cuts and tax increases in return for more financial aid.

Greece's creditors had asked for major reforms and spending cuts in exchange for extending its bailout deal until November in an offer worth several billion euros.

When talks between the government and creditors collapsed last week, the extension was refused and the bailout ended as scheduled on 30 June.

Greeks have therefore been voting on an offer which is no longer on the table.

Many shoppers have been panic buying from supermarkets - purchasing essentials such as pasta and flour - as the country's fate unfolds.

On Friday, Greece was officially declared in default by the European Financial Stability Facility - days after the nation fell into arrears with the IMF.

Banks across the country have been closed over the past week, with customers only able to withdraw €60 a day from cash machines.

Earlier, when Greek Finance Minister Yanis Varoufakis arrived at a polling station in Athens, he was asked by Sky News why people should believe him when he said the banks would re-open on Tuesday when they were running out of money.

He replied: "You're spoiling a celebration with impertinent questions."

When asked again, he was silent.

Experts say Greece's banks will not be able to open unless they receive further cash from the EU.

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