Greek Finance Minister Yanis Varoufakis has accused Athens' creditors of "terrorism", the day before a referendum on an international bailout.
Speaking to Spain's El Mundo newspaper, he said the country's lenders wanted to "instil fear in people".
Huge rallies were held by both sides in the referendum on Friday night.
The government has urged voters to say "No" to the terms of a bailout package, but opponents warn that this would see Greece ejected from the eurozone.
Greece's current bailout programme with the European Commission, International Monetary Fund (IMF) and European Central Bank (ECB) ran out on Tuesday.
Banks have been shut all week, with limits imposed on cash withdrawals.
The BBC's Chris Morris in Athens says that, for many, this has become a choice about whether to stay in the eurozone. With so much at stake, he says, the rhetoric is getting nasty.
Mr Varoufakis said the so-called "troika" of creditors wanted a "Yes" vote to win so they could humiliate the Greeks.
"Why did they force us to close the banks? To instil fear in people. And spreading fear is called terrorism," he said.
He added that Greek Prime Minister Alexis Tsipras would still reach an agreement with creditors if the result was "No", and that banks in Greece would reopen on Tuesday whatever the outcome.
Correspondents say it is unclear whether this will happen.
"The EU will have no legal grounds to throw Greece out of the euro, and then the real negotiation will start with creditors," Mr Varoufakis told Greek newspaper Kathimerini.
German Finance Minister Wolfgang Schaeuble, one of Greece's harshest critics, suggested that if Greece were to leave the eurozone, it might only be temporary.
"Greece is a member of the eurozone. There's no doubt about that," he told German newspaper Bild.
"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."
Tens of thousands of Greeks attended the rival rallies on Friday night.
Mr Tsipras told supporters Greece needed "say a proud 'No' to [European] ultimatums" to sign up to fresh austerity.
But he also used similar language to Mr Varoufakis, urging Greeks to "say 'No' to ultimatum, to blackmail, to the campaign of terror".
He denied a "No" vote would mean leaving the European Union - though opponents said they believed Mr Tsipras could not deliver on such a promise.
Opinion polls on Friday suggested the country was evenly split. An Ipsos survey put "Yes" supporters at 44% and "No" at 43%.
Opinion polls within 24 hours of the voting are banned, as are rallies.
Greece's left-wing Syriza government was elected in January on an anti-austerity platform.
The European Commission, the European Union's executive arm - one of the "troika" of creditors along with the International Monetary Fund and the ECB - wants Athens to raise taxes and slash welfare spending to meet its debt obligations.
On Tuesday, the previous eurozone bailout expired, depriving Greece of access to billions of euros in funds, and Athens missed a €1.5bn (£1.1bn) repayment to the IMF.
