Thousands of people rallied in Athens Tuesday in support of a bailout deal with international creditors which has been rejected by Prime Minister Alexis Tsipras, leaving Greece on the brink of default.

At least 20,000 people, many waving European and Greek flags and blowing whistles, gathered in front of parliament in Syntagma square five days before a referendum on whether or not to accept the bailout.

The cry "resign!" sounded repeatedly through the crowds, with families, businessmen and the retired braving the rain to vent their anger against Tspiras and his radical left Syriza party.

Negotiations with Athens's creditors fell apart after Tsipras called a shock referendum on their proposals, and demonstrators were furious too with Finance Minister Yanis Varoufakis.

"Don't you Varoufuck Greece" read one banner held aloft, while another read "Greece is Europe".

Tspiras was forced to impose capital controls after news of the breakdown in talks sent anxious Greeks rushing to ATMs to withdraw their savings in case of a Greek exit from the eurozone.

Banks shut their doors for a week, while withdrawals at cash machines were topped at 60 euros ($66).

"The banks will re-open on Sunday, and they will reopen with the Drachma," said Polivias, a civil engineer, referring to the currency used in Greece before it joined the euro in 2001.

The radical left, which came to power in January promising a new bailout deal, insists Greece has suffered enough austerity, with Tsipras accusing international creditors of wanting to "humiliate" the country.

But critics say the premier has worsened the situation by scuppering negotiations over the bailout and declaring his intention to put the latest offer from Greece's creditors to popular vote.

A request for a bailout extension was refused, and the country was set to miss a key deadline Tuesday to repay money to the International Monetary Fund (IMF), sparking fears of further financial mire to come.

Lawyer Vassiliki Salaka said those in charge of Greece now were "incompetent, they lack organisation, they don't know what they want".

Around 200 anti-establishment protesters tried to join the rally but were pushed back by police in riot gear, who closed off side streets near Syntagma square.

"Europe is our family. European values are Greek values. There are huge difficulties, but bankruptcy and making the country like North Korea is catastrophic for everyone," lawyer Dionisis told AFP TV.

Fellow demonstrator Ipapadim agreed, saying life "will be difficult inside or outside (the eurozone), but we can't go where Tsipras and Varoufakis want, to lead the country without a plan B... by the roll of a dice".

Tuesday's rally came a day after 17,000 people took to the streets of Athens and Thessaloniki to support Tsipras, saying they would heed his call to vote against the latest deal in Sunday's referendum -- despite risks it could send the country crashing out of the eurozone.