Brussels: Greek Prime Minister Alexis Tsipras has vowed to press ahead with a controversial bailout referendum as European leaders ruled out any fresh debt offer before Sunday's vote.

Hours after Greece became the first advanced economy to default on an International Monetary Fund (IMF) repayment, the leftist leader used a live TV address yesterday to urge Greeks to vote 'No' on Sunday to creditors' current demands.

Tsipras, at loggerheads with Greece's creditors since his election in January, insisted a 'No' vote would "not signify a rupture with Europe" despite efforts by EU leaders to cast it as a referendum on Greece's place in the bloc.

"Come Monday, the Greek government will be at the negotiating table after the referendum, with better terms for the Greek people," he added, standing between Greek and EU flags.

His comments came after Greece on Tuesday made a last-minute proposal for a third bailout worth nearly 30 billion euros (USD 33 billion) to follow the two rescue programmes worth 240 billion euros cash-strapped Athens has received since 2010.

Frustrated eurozone finance ministers agreed yesterday to wait until after the referendum before holding any more talks, saying there were "no grounds" for further discussions.

EU officials consider a 'No' vote as a risky step towards a possible exit of Greece from the eurozone and the beginning of an unprecedented crisis for the bloc.

On Greece's streets, chaotic scenes ensued when nearly 1,000 banks reopened yesterday to allow elderly people limited access to their pensions after several days of capital controls limiting withdrawals.

"I worked for 50 years on the sea and now I am a beggar for 120 euros," one pensioner in Athens said. "I have no money for medication for my wife, who had an operation and is ill."

Ahead of the referendum, an opinion poll yesterday showed the 'No' camp in the lead with 46 per cent, against 37 per cent for 'Yes' and 17 per cent undecided. The 'No' vote share was down compared to before capital controls were introduced Sunday.

The Council of Europe, a pan-European human rights body, has criticised the vote, saying it was being organised too quickly and that the question was not clear.

Greece entered uncharted waters with its default on the 1.5-billion euro IMF loan and expiry of its current European bailout on Tuesday.

It is now without external financial assistance for the first time in five years. The developments prompted Moody's to cut its credit rating for Greece to a deep-junk "Caa3" - the last of the three major ratings agencies to do so - warning it was now less likely that official creditors will support the country, whatever happens in Sunday's referendum.