Campaigns halt in Greece on Saturday on the eve of a closely watched bailout referendum — with voters in a dead heat over whether to defy creditors and push for better repayment terms or essentially seek new political leadership to find a compromise.

Political rallies and publication of new opinion polls are banned 24 hours before Sunday's referendum called by left-wing Prime Minister Alexis Tsipras, who has promised to ease austerity after six years of recession.

Rival rallies took place a half-mile apart in central Athens late Friday, and Tsipras made his final pitch on a stage set up for a campaign rock concert outside parliament.

"This is not a protest. It is a celebration to overcome fear and blackmail," he told a crowd of 30,000 as they roared oxi, oxi— "no, no."

The 40-year-old Tsipras is gambling the future of his new left wing government on Sunday's snap poll — insisting a "no" vote will strengthen his hand to negotiate a third bailout with better terms.

If he loses, Tsipras has strongly indicated he would step aside.

Athens' high-stakes standoff with lenders saw Greece default on debts this week, close banks to avoid their collapse, and lose access to billions of euros after an existing bailout deal expired.

The EFSF, the Eurozone's rescue fund and Greece's largest creditor, said Friday it considered the country to be in default.

At Friday's "no" rally, Athens resident Maria Antoniou held a handmade sign, reading "oxi."

"We have to strengthen Tsipras. It's not his fault we are bankrupt," she said.

"He doesn't have the mandate to take tougher measures and now we are giving that to him. It's not true this is a vote on the euro. It's a vote to change course and stay in the euro, and Tsipras is our best hope," she said.

That is a message the "yes" voters refuse to believe.

Police said about 22,000 people gathered outside the nearby Panathenian stadium for the "yes" rally, waving Greek and European Union flags and chanting "Greece, Europe, Democracy."

Evgenia Bouzala, a Greek born in Germany, said she was considering shutting down her olive oil export business because of the financial turmoil.

"I don't think we can keep going. Look at what happened in the last three days. Imagine if that lasts another six months," she said.

"A 'yes' vote would bring a caretaker government and that would probably be better ... We have to start over."

Rallies for both campaigns were also held in 10 other Greek cities Friday, and the drama remained high in the final hours of campaigning.

The country's top court stayed in session till the late afternoon before rejecting a petition to declare the referendum illegal. Political party leaders, personalities, and even church elders weighed in with impassioned pleas to vote "no" or "yes" on the airwaves and social media.

In a rare public declaration, 16 former armed forces leaders wrote an appeal to citizens to show "calm and national unity."

A series of polls published Friday at the end of a frantic weeklong campaign showed the two sides in a dead heat, with an incremental lead of the "yes" vote well within the margin of error.

They also showed an overwhelming majority of people — about 75 percent — want Greece to remain in the euro currency.

Much of the ambiguity arises from the complicated question on the ballot paper:

"Must the agreement plan submitted by the European Commission, the European Central Bank and the International Monetary Fund to the Eurogroup of 25 June, 2015, and comprised of two parts which make up their joint proposal, be accepted? The first document is titled 'reforms for the completion of the current program and beyond' and the second 'Preliminary debt sustainability analysis.'"

Voters are asked to check one of two boxes: "not approved/no" and — below it — "approved/yes."

"People don't even understand the question," Athens Mayor George Kaminis told supporters at the "yes" rally.

"We have been dragged into a pointless referendum that is dividing the people and hurting the country."

Greek Finance Minister Yanis Varoufakis told Ireland's RTE radio Friday that an agreement with creditors "is more or less done" and that the only issue left is debt relief.

But Germany's finance minister, Wolfgang Schaeuble told his country's Bild daily that any negotiations after the Greek vote "will take a while."

Jeroen Dijsselbloem, the head of the eurozone finance ministers' group, noted that negotiations had been broken off.

"There are no new proposals from our side and, whatever happens, the future for Greece will be extremely tough," he said.

"To get Greece back on track and the economy out of the slump, tough decisions will have to be taken and every politician that says that won't be the case following a 'no' vote is deceiving his population."