Greek Prime Minister Alexis Tspiras has "torn down the bridges" between Greece and Europe and new negotiations are "difficult to imagine" after the apparent 'No' vote in the Greek referendum, German deputy chancellor Sigmar Gabriel said on Sunday.

Tsipras and his government are taking Greece down a path of "bitter renunciation and hopelessness," Gabriel told the Tagesspiegel newspaper in the first high-level reaction from the German government.

Greece has moved a step closer towards a eurozone exit, Russia's deputy economy minister said Sunday, as early results from a crucial bailout referendum suggested Greeks had overwhelmingly rejected creditors' demands for more austerity.

"You can't fail to understand" that this means "a step towards an exit from the eurozone", Alexei Likhachev was quoted as saying by the state TASS news agency.

Greece will have to introduce another currency if it votes 'No' in Sunday's referendum on its potential bailout terms, European Parliament president Martin Schulz said on German radio.

He told Deutschlandfunk that, in the event of a 'No' result, Greece would "have to introduce some other currency because the euro is not available as a means of payment."

Hamas authorities on Sunday reopened the offices of the Gaza Strip's only mobile telephone company, five days after closing them on accusations of tax-dodging.

A statement from attorney general Ismail Jaber's office said that he had "ordered the reopening" of telecom provider Jawwal in Gaza City, but it did not give reasons.

Greece's government on Sunday looked to have won a 'No' it had been seeking in a referendum on bailout terms, but the euro immediately plummeted on fears the result could splinter the eurozone.

An official tally of over half the ballots cast showed a resounding 61 percent of Greek voters had backed the government's 'No' in the plebiscite. 

Tourists are vital to Barcelona's economy, but the 27 million people who visit each year have become a headache for the new mayor as she battles to save the iconic Spanish Mediterranean port from becoming a bland theme park.

"Tourists go home" is frequently found painted on the walls of buildings in the center of Spain's second-largest city, which is struggling to cope with a surge in tourism that started when it hosted the Olympics in 1992.

In the five months since he came to power vowing to deliver his country from years of biting austerity, Prime Minister Alexis Tsipras has kept Greece and Europe guessing.

For some he is a master strategist who has called the bluff of Greece's creditors by giving the people the final say on a painful debt deal.

German Chancellor Angela Merkel and other EU leaders await with trepidation the outcome of a referendum in Greece Sunday that is already dividing opinion in Europe and could even shape its future.

After months of fruitless talks with its creditors, Greece's dramatic bid to place a bailout decision in the hands of its people will have an impact far beyond the heavily-indebted country's borders, analysts warn.

Greece braced itself Saturday ahead of a make-or-break bailout referendum as polls showed the 'Yes' and 'No' camps neck and neck and uncertainty rose over the future of the country's battered economy.  

Prime Minister Alexis Tsipras got a rock-star welcome at an Athens rally late Friday as he sought to revive support for a 'No' vote in a referendum called to strengthen his hand in talks with international creditors.

Greece was officially declared in default on Friday, injecting even more urgency into a make-or-break weekend referendum that new polls suggested was too close to call.

The fund providing Greece's financial lifeline declared "an event of default by Greece."