The gloves are off for French centrist candidate Emmanuel Macron and his far-right rival Marine Le Pen after his win in Sunday's first- round voting lifted the spirits of France's European Union neighbours and financial markets.

Mr Macron, 39, has emerged as the clear favourite to become the country's youngest president after securing 23.75 per cent of the votes on Sunday. Ms Le Pen, 48, of the National Front had 21.53 per cent.

EU officials in Brussels, in a break with protocol, were quick to congratulate Mr Macron.

With 10 more days of campaigning to go - and a live television debate scheduled for May 3 - before the final round of voting on May 7, both candidates have a lot of work to do to rally support.

The dejected French establishment, rejected by French voters on Sunday, quickly rallied around Mr Macron yesterday, telling supporters to vote for him and see off Ms Le Pen, who has vowed to take France out of the EU.

Mr Macron, who leads the new political movement En Marche! (On the Move), late on Sunday told supporters, who were chanting "Macron president!", that he was humbled by the "tremendous responsibility thrust upon me".

Striking an internationalist note, he said he offered "a new path for hope, for Europe, for the world".

His first-round win sparked a stock market rally yesterday, especially for euro zone bank shares, and the euro surged to its strongest level against the US dollar since last November.

Ms Le Pen's National Front went on the attack, calling Mr Macron, a former banker, a "candidate of oligarchs" and banking lobbies who rubs shoulders with celebrities.

Earlier, speaking to her supporters, Ms Le Pen vowed to fight against globalisation, dismissing Mr Macron as the heir to France's outgoing President Francois Hollande.

Mr Macron was economy minister in the outgoing Socialist administration, but he was appointed to the role and has never been elected to any position, making him the insider's outsider.

Ms Le Pen, sounding not unlike United States President Donald Trump, returned to her themes of opposition to "wild globalisation" and the fight against terrorism yesterday, which she feels give her an advantage over her mainstream rival.

Mr Macron, who proposes economic liberalisation, did not shy away from confronting Ms Le Pen head-on, declaring: "Nationalism is war."

The relief in Brussels prompted European Commission chief Jean- Claude Juncker and EU diplomatic chief Federica Mogherini to phone Mr Macron to congratulate him.

"Last night, there was one choice between what Europe actually represents and a choice that represents the destruction of Europe," a spokesman for Mr Juncker said in defence of the decision to make the congratulatory phone call.

Mr Macron's victory is now widely believed to be a fait accompli: A poll published by Opinionway yesterday predicts that he will win 61 per cent of the vote against 39 per cent for Ms Le Pen on May 7.

"Do we have reliable certainty that Macron will win the second round? The answer is yes. It would be very surprising to see Marine Le Pen win. Our polls have an average of 60 per cent for Emmanuel Macron right now," said Mr Emmanuel Riviere, chief executive of research firm Kantar Public.

The unlikely pair will face off in the final televised debate on May 3 - and there are likely to be fireworks, with Ms Le Pen doubling down, following her winning her party's highest-ever share of the vote.

Despite his insurgent campaign, Mr Macron is considered more a continuity candidate than a radical. Still, there has been a major shift in French politics, with neither of the two parties that have governed the country since the end of World War II - the Republicans and the Socialists - in the running for the presidency.

At stake on May 7 is not only France's place in the world, but the future of the already frayed post- war European political order.

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