Tens of thousands of Greeks have attended rival rallies in Athens ahead of a crucial referendum on Sunday.

Prime Minister Alexis Tsipras was greeted with huge cheers when he told supporters to vote "No" to the terms of an international bailout.

But those attending another huge rally nearby warned a "No" vote would see Greece ejected from the eurozone.

A Greek court earlier rejected a challenge to the legality of the referendum and it will go ahead.

Greece's current bailout programme ran out on Tuesday. All week banks have been shut, with limits imposed on cash withdrawals.

The BBC's Chris Morris in Athens says this has become a choice about whether to stay in the eurozone. With so much at stake, he says, the rhetoric is getting nasty - no-one can even be sure whether Greek banks will be able to reopen next week as the government has promised.

Another war of words flared late on Friday when Finance Minister Yanis Varoufakis dismissed a Financial Times report that Greece was preparing contingency plans for a possible "bail-in" of bank deposits as a "malicious rumour". The report quoted sources as saying banks were considering a "haircut" of 30% on deposits over €8,000.

Opinion polls suggest the country is evenly split over the vote - the latest Ipsos survey putting "Yes" supporters at 44 petrcent and "No" at 43 percent.

'ARMAGEDDON'

Estimates of the crowds gathered in Athens ranged from 25,000 to 50,000, with police and observers agreeing that the crowds at the "No" rally were bigger.

Rallies for both camps were held in 10 other Greek cities.

In his speech on Friday night, Tsipras reiterated the themes of almost daily addresses over the past week - the need for Greece to preserve its dignity and "say a proud 'No' to [European] ultimatums" to sign up to fresh austerity.

He said: "This is not a protest. It is a celebration to overcome fear and blackmail."

Tsipras urged Greeks to "decide to live in dignity in Europe".

He denied a "Yes" vote would mean leaving Europe, saying: "We are not going to allow them to destroy Europe."

But only a few hundred metres away, supporters of a "Yes" vote said they believed Mr Tsipras could not deliver on such a promise.

Nikos, a doctor, told AFP: "They cannot pretend any longer that it's not about leaving the euro... and outside the euro lies only misery."

BALLOT PAPER QUESTION

"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 programme and beyond" and the second "Preliminary debt sustainability analysis".

Voters must check one of two boxes - "not approved/no" or, below it, "approved/yes"

VOICES FROM A GREEK ISLAND

Unemployed economist Marina Peppa, 45, told Reuters: "It's not going to be easy, but if 'No' prevails, we'll have Armageddon, total poverty."

Athens Mayor George Kaminis told supporters at the rally that people did not even understand the question on the ballot paper.

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

Claims by Greek politicians that a "No" vote will strengthen their hand in bailout negotiations have been rebuffed by European leaders.

Both EU Commission President Jean-Claude Juncker and Jeroen Dijsselbloem-head of the Eurogroup of finance ministers - have insisted a "No" vote will weaken the Greeks' position and that even a "Yes" vote will not mean a deal is easy to agree.

Dijsselbloem 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."

Several European officials have complained in strong terms about Greece's abrupt decision to hold a referendum on the terms of a bailout offer they say is no longer on the table.

In a ruling on Friday, Greece's top administrative court rejected an appeal lodged by two individuals who had argued that it was illegal to hold popular votes on fiscal matters.

The European Commission, the European Union's executive arm - one of the "troika" of creditors along with the International Monetary Fund and the European Central Bank - 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 repayment to the IMF.

LENDERS' PROPOSALS: KEY STICKING POINTS

VAT (sales tax): Alexis Tsipras accepts a new three-tier system, but wants to keep 30% discount on the Greek islands' VAT rates. Lenders want the islands' discounts scrapped.

Pensions: Ekas top-up grant for some 200,000 poorer pensioners will be phased out by 2020 - as demanded by lenders. But Tsipras says no to immediate Ekas cut for the wealthiest 20 percent of Ekas recipients

Defence: Tsipras says reduce ceiling for military spending by €200m in 2016 and €400m in 2017. Lenders call for €400m reduction - no mention of €200m.