He said “democracy” won in Greece.

He also changed his Twitter picture to one showing himself at a rally with Greek PM Alexis Tsipras.

Rafael Mayoral, a fellow Podemos leader, who was in Athens on Sunday (5 July), said “joy is in the air”.

Gabi Zimmer, the president of the far-left Gue group in the European Parliament, in her statement also attacked the “EU’s ruling elites”.

Naming German finance minister Wolfgang Schaeuble, she spoke of an “unprecedented campaign of fear” against Greek voters.

But her main message was that the EU should give Greece debt relief for “political” reasons, in order to keep the Union together.

“Greeks are … saying Yes to European integration and Yes to European democracy”, she wrote.

For her part, Marine Le Pen, the leader of the far-right National Front party in France, on Sunday welcomed Greece’s “beautiful” lesson in democracy.

But, unlike Zimmer, she said it means “the failure of the euro”.

She urged EU leaders to sit “around the negotiating table, take stock … and organise the dissolution of the single currency”.

She told Sud Radio on Monday that the EU is a kind of "sect" which "brainwashes" people and compared the eurozone to a "European Soviet Union".

Florian Philippot, one of her senior aides, told BFM TV the No means the "infernal machine" of the EU "isn't irreversible".

Geert Wilders, the leader of the Dutch anti-immigrant party, the PVV, tweeted that the Netherlands will quit the euro after Greece does: “No = Grexit. After that Nexit”.

His British counterpart, Nigel Farage, the leader of the anti-immigrant Ukip party, went further.

He said the No means the “EU project is now dying”.

There were few international reactions on Sunday evening, as leaders prepared snap meetings to digest the result.

But Alexei Likhatchev, Russia’s economy vice-minister, joined Le Pen and Farage in wishing the euro ill.

Greece has “taken a step towards leaving eurozone”, he said, according to Tass, a Russian state mouthpiece.