France's incumbent leader Emmanuel Macron has urged citizens to block his far-right challenger Marine Le Pen from power when the two go head-to-head in a 24 April presidential run-off vote, adding that "nothing is decided" yet.

In a speech to his supporters, Mr Macron pledged he would work to convince all voters, including those who abstained or voted for candidates on the far-right and hard left, to vote for him.

"Make no mistake: nothing is decided. The debate that we are going to have over the next fortnight will be decisive for our country and Europe," he added.

Mr Macron garnered 28.1-29.5% of votes in today's first round while Ms Le Pen won 23.3-24.4%, according to separate estimates by pollsters Ifop, Opinion Way, Elabe and Ipsos. Those estimates, published as voting ended, are usually very reliable in France.

If confirmed, that outcome would set up a duel between an economic liberal with a globalist outlook in Mr Macron and a deeply eurosceptic economic nationalist in Ms Le Pen who, until the Ukraine war, was an open admirer of Russian President Vladimir Putin.

Marine Le Pen addresses supporters after the results in Paris this evening
Marine Le Pen addresses supporters after the results in Paris this evening

Who next holds the Elysee Palace will depend on how those who backed Mr Macron and Ms Le Pen's rivals cast their ballots.

Conservative candidate Valerie Pecresse, the Socialists' Anne Hidalgo, the Greens' Yannick Jadot and the Communists' Fabien Roussel said they would back Mr Macron to block the far-right.

"So that France does not fall into hatred of all against all, I solemnly call on you to vote on April 24 against the far-right of Marine Le Pen," said Ms Hidalgo.

Ms Pecresse warned of "disastrous consequences" if Mr Macron did not win the runoff.

But another far-right candidate Eric Zemmour will call on supporters to back Ms Le Pen, Marion Marechal - who is an ally of Mr Zemmour and Ms Le Pen's niece - told BFM TV.

To cheers of supporters chanting "We will win! We will win!," Ms Le Pen said she wanted to unite all French. The runoff "will be a choice of civilisation," she said, adding that her platform would protect the weak and make France independent.

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Not for two decades has a French president won a second term.

Barely a month ago, Mr Macron was on course to comfortably reverse that, riding high in polls thanks to strong economic growth, a fragmented opposition and his statesman role in trying to avert war on Europe's eastern flank.

But he paid a price for late entry into the campaign during which he eschewed market walkabouts in provincial France in favour of a single big rally outside Paris. A plan to make people work longer also proved unpopular, enabling Ms Le Pen to narrow the gap in opinion polls.

By contrast, Ms Le Pen toured towns and villages across France for months, focusing on cost-of-living issues that trouble millions and tapping into anger towards the political elite.

After a more than 10-point lead Mr Macron had enjoyed as late as mid-March, voter surveys ahead of the first round showed his margin of victory in an eventual runoff whittled down to within the margin of error.

The hard left's Jean-Luc Melenchon polled third today with an estimated 20%, the projections showed.

A Le Pen victory on 24 April would constitute a similar jolt to the establishment as Britain's Brexit vote to leave the European Union or Donald Trump's 2017 entry into the White House.

France, the EU's second largest economy, would lurch from being a driving force for European integration to being led by a eurosceptic who is also suspicious of the NATO military alliance.

While Ms Le Pen has ditched past ambitions for a 'Frexit' or to haul France out of the eurozone's single currency, she envisages the EU as a mere alliance of sovereign states.

In past French elections in 2002 and 2017, voters on the left and right have united to block the far-right from power.

However, surveys suggest that the so-called republican front' has crumbled, with many left-wing voters saying they are loathe to endorse a leader they deride as arrogant and a 'president of the rich'.