Greek Prime Minister Alexis Tsipras has urged Greeks to reject 'blackmail' when they vote on whether the country accepts the terms of a bailout agreement on Sunday.

They have the power to decide whether Greece accepts harsh austerity measures in exchange for fresh funds or plunges deeper into an economic abyss.

Its banks have been shut all week, cash withdrawals have been rationed and now EU leaders have warned that a 'No' vote could result in Greece leaving the European Union.

But in a short TV address, Tsipras told voters to reject the 'sirens of scaremongering' and said Greece's presence inside the EU was not at stake.

The country's total debt stands at a staggering £229billion and three quarters of that is owed to the EU, the European Commission and the International Monetary Fund (IMF).

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Defiant: Greek Prime Minister Alexis Tsipras (pictured) has urged Greeks to reject 'blackmail' when they vote on whether the country accepts the terms of a bailout agreement on Sunday

Tears: Greek pensioners have been queuing at some banks, closed to everyone else, since before dawn to get their money which the Greek Banks Union says will run out on Monday

Hard times: Its banks have been shut all week, cash withdrawals have been rationed and now EU leaders have warned that a 'No' vote could result in Greece leaving the European Union

Austerity: An elderly man finds old clothes as he searches in a garbage bin in the northern Greece ahead of the crucial vote on Sunday

The head of the Greek Banks Union says the country's banks have a cushion of €1bn until Monday morning and after that, it is at the mercy of the European Commission Bank.

Meanwhile, tourists have been warned they could be left without food or access to medicines 'within days'

Tsipras defended the weekend referendum which he hopes will reset these bailout negotiations and rescue his nation from economic turmoil.

The leader of the radical left Syriza party - which governs Greece in a ruling coalition - demanded that creditors forgive a third of Greece's debt and allow a delayed repayment of the rest.

The vote is 'a time of responsibility and democracy meant to silence the sirens of destruction,' he said in a TV address.

He added: 'Rejecting an unsustainable agreement does not mean a break with Europe... We will face a common future on Monday and we will not allow anything to divide us.'

The country is almost split ahead of the crucial vote 44.8 per cent planning to vote 'Yes' and accept the EU's demands and 43.4 per cent will vote no, according to a survey by the Alco institute. But its error margin of plus-or-minus 3.1 per cent makes it too close to call.

Creditors want voters to vote 'Yes' and accept austerity measures in return fore rescue loans but Prime Minister Tsipras called on voters to vote 'no to ultimatums, divisions and fear'.

Panic: Huge queues have been building outside banks as people wait to get their state pension

Crisis: A pensioner receives part of her pension outside a bank in Athens today where desperate elderly people without ATM cards have been queuing up outside banks

Desperate: Pensioners are given priority tickets as they wait to receive part of their pensions in Athens this morning

Fightback: A woman makes her way past referendum campaign posters in Athens which read: 'No'

Tsipras says a recent report by the International Monetary Fund report - which says Greece needs debt relief - is a 'great vindication' that his government's position that its debt is unsustainable.

Tsipras said it was pointless to continuously impose harsh spending cuts on salaries and pensions just to keep servicing the out-of-control debt.

As anger mounted and queues at cash machines got longer, he promised voters that banks would re-open as soon as the government clinched a new loan deal from the eurozone.

He condemned the 'humiliating' terms Greece was offered by international creditors last week - in a deal that is no longer on the table.

The programme that they imposed upon this country and which they want to continue imposing... is going to come down in economic history as the greatest cock-up ever Yanis Varoufakis, Greek Finance Minister

Meanwhile his Finance Minister Yanis Varoufakis has condemned the policy of austerity imposed on Greece over the last five years as a 'travesty'.

Varoufakis promised to step down if the country votes 'Yes' and insisted a 'No' vote would relaunch the country's negotiations with its international creditors.

But he told the BBC on Thursday 'an agreement will be reached' either way, adding: 'We have a very bad system of governance in Europe. This is not the way to run a monetary union.

'This is a travesty. It's a comedy of errors for five years now, Europe has been extending and pretending.

'The programme that they imposed upon this country and which they want to continue imposing... is going to come down in economic history as the greatest cock-up ever.'

The Greek economy is being squeezed having lost access to fresh funds, while banks have shut down and imposed strict limits on how much money can be withdrawn from cash machines.

German Chancellor Angela Merkel has refused to engage in further negotiations until after Sunday's vote.

The vote on Sunday could determine whether Greece becomes the first country to crash out of the 19-nation European single currency area. Membership in the group is meant to be irrevocable.

Agreement: German Chancellor Angela Merkel is refusing to hold further negotiations with Greece until after the referendum

Pledge: Greece's finance minister Yanis Varoufakis (pictured) says he'd rather 'cut off his arm' than agree to the latest debt deal

Ordeal: Varoufakis has condemned the policy of austerity imposed on the Greek people (pictured) over the last five years as a 'travesty'

A survey has found that 74 per cent of Greeks want to stay in the euro while just 15 percent want to return to a national currency - with 11 percent undecided.

Credit ratings agency Fitch said the banks were already effectively bust and would fail within days unless the European Central Bank helps them cope with a wave of withdrawals.

There has been little time for campaigning but Tsipras is due to address a mass rally of 'No' supporters in Athens' central Syntagma Square outside parliament on Friday evening, while 'Yes' campaigners plan a rally at the old Olympic Stadium.

The 'No' campaign has directed much of its venom at Germany, the euro zone's dominant power and Greece's biggest creditor.

One poster plastered in central Greece shows a picture of German Finance Minister Wolfgang Schaeuble with the slogan: 'For five years he's been sucking your blood. Tell him 'No' now.'

Greek websites are reporting that a supermarket in Athens has been looted by anarchists who threw 'No' posters through the window.

But Greek expats are reportedly hurrying back to the country - and mostly voting 'yes'.

Upcoming vote: More elderly line up outside a bank in Athens to receive their pensions today ahead of a weekend referendum on whether Greece should accept austerity measures proposed by the eurogroup

On the verge of leaving the eurozone: Greece is in a financial limbo now that its bailout program has expired, cutting it off from vital financing and pushing it one step closer to leaving the euro

Deepening crisis: The referendum has thrown additional confusion into the already fraught negotiations

Konstantinos Dimitriou, a management consultant who now lives in Singapore, is catching a plane early on Saturday to make the 19-hour journey back to Athens to vote 'Yes' to accept a deal.

'All the opportunities I got in my life to grow came in part from Greece's relationship with Europe, not just my Greek passport,' he said.

And Endy Zemenides, executive director of the Hellenic American Leadership Council, said: 'I know people who are stocking up on staples, like medications, to take to older relatives.'

Aegean Airlines is putting on extra flights to and from Brussels and London Stansted - as well as offering return seats in economy class for £148 to and from London without a suitcase.

'The tickets to go to Greece this weekend are really expensive,' said Dimitri Augustidis who runs a tourism website in Britain and is heading back himself.