Greece's finance minister accused creditors of trying to "terrorise" Greeks into accepting austerity, warning Europe stood to lose as much as Athens if the country is forced out of the euro after a referendum on Sunday on bailout terms.

After a week in which Greece defaulted, shuttered its banks and began rationing cash, Greeks vote on Sunday on whether to accept or reject tough conditions sought by international creditors to extend a lending lifeline that has kept the debt-stricken country afloat.

The left-wing government is urging a 'No' vote, saying Greece's European partners are bluffing when they warn that would mean a Greek departure from Europe's single currency, with unforeseeable consequences for Greece, Europe and the global economy.

Opinion polls on Friday gave the 'Yes' camp, which favours accepting the bailout terms, a slender lead but all were within the margin of error and pollsters said the vote was too close to call.

Only one had the 'No' vote winning, despite a turnout of at least 50,000 opponents of the deal at a rally in central Athens on Friday that appeared significantly bigger than a simultaneous rally by the 'Yes' camp.

"What they're asking us to accept is eternal slavery," said Ermioni Tenekidou, 54, a teacher.

Finance Minister Wolfgang Schaeuble of Germany, Greece's biggest creditor and toughest critic, said any so-called Grexit, Greek exit from the euro zone, might only be temporary.

"Greece is a member of the euro zone. There's no doubt about that. Whether with the euro or temporarily without it: only the Greeks can answer this question. And it is clear that we will not leave the people in the lurch," he said.

But it is far from clear how a temporary exit from the 19-nation euro currency bloc might work. Some economists have raised the idea of a temporary suspension, whereby Greece would revert to a national currency for a number of years until its economy stabilised.

Greece's European partners say the euro zone is better placed to minimise the impact on its vulnerable southern flank from a Greek exit than several years ago when the debt crisis exploded. But Greek Finance Minister Yanis Varoufakis said Europe stood to lose more than Greece.

"If Greece crashes, a trillion euros (the equivalent of Spain's GDP) will be lost. It's too much money and I don't believe Europe could allow it," he told Spanish newspaper El Mundo.

Varoufakis reiterated he would resign if Greeks vote 'Yes', and accused creditors of trying to terrorise voters by capping a liquidity line to Greek banks.

"What they're doing with Greece has a name: terrorism," he told El Mundo. "Why have they forced us to close the banks? To frighten people."-Reuters