French voters are heading to the polls after a tumultuous presidential election race that has captivated international observers and turned the country’s political landscape upside down.

Centrist Emmanuel Macron, who has never been elected to a public office, is expected to win the presidency over his far-right rival Marine Le Pen, after extending his 20-point poll lead in the final hours of the campaign.

The election is seen as one of France’s most important in decades with two candidates with diametrically opposed views on France’s place in the European Union and the world going head to head.

A staunch Europhile, Mr Macron says he will strengthen EU cooperation and maintain an open economy while Ms Le Pen has pledged to quit the euro, hold a referendum on France's membership of the union and bring in protectionist trade policies.

Emmanuel Macron at a campaign meeting in Albi, southwestern France, on Thursday (Getty)

A focal point of the campaign was the bitter televised debate on Wednesday, when the two candidates attacked each other with a string of barbs and insults.

The election is seen as a test of the strength of populist movements in Europe and on the appetite for France’s own referendum on the EU. But above all voters have so far made clear their desire for change in the country’s political arena.

France’s two traditional parties, which have held power in the Élysée Palace for decades, were knocked out in the first round of the election on 23 April while politically extreme parties together received more than 40 per cent of the votes.

In the month preceding the election’s first round, conservative François Fillon became mired in corruption scandal over payments to his wife and children for work they allegedly have not done. The saga meant his right-wing Republican party did not contest the second round of the election for the first time.

Boxes of ballot papers at the City Hall in Montreuil, outside Paris, yesterday (Getty)

The crisis of French politics has left many voters feeling the choice is one of the lesser of two evils, with many saying they would rather spoil their ballot than endorse either candidate.

On the one hand, Mr Macron, a former investment banker for Rothschild and minister of the economy in the Socialist government, has been accused of defending the interests of the financial sector.

A year after launching his own movement En Marche! (Let’s Go!), Mr Macron has been fighting accusations that he is just more of the same despite attempts to portray him as a candidate for change. The 39-year-old, who has been accused of political immaturity, could become France’s youngest elected president.

On the other hand, Ms Le Pen has capitalised on a growing anti-EU sentiment and working-class voters’ frustration over globalisation and immigration.

Despite Ms Le Pen’s efforts to relinquish her party’s former image of Holocaust denial and racism, French newspapers have suggested the far-right candidate is no different.

Earlier this month, Ms Le Pen crossed a red line when she said France was “not responsible for the events of the Vel d’Hiv”, referring to the mass arrest of 13,000 Jews by French police in Paris in 1942. They were then transported to Nazi extermination camps.

Marine Le Pen at a campaign meeting in Ennemain, northern France, on Thursday (Getty)

On its Friday front page, the Liberation newspaper splashed a black-and-white picture of Ms Le Pen’s father Jean-Marie, who was convicted of inciting racial hatred after saying gas chambers were “a detail” of the Second World War, with the words: “She [Ms Le Pen] has not changed."

Crowds roared “neither Marine, nor Macron” and “neither banker, nor fascist” during demonstrations across France between the two rounds of the election, when a few hundred protesters clashed with police forces.

Participation is going to be a key issue in the final run-off with a high level of abstention potentially helping Ms Le Pen narrow the gap on her rival.

In the final days of the campaign, The Independent spoke to voters in Paris and its surroundings, where many remained undecided and unconvinced by the candidates.

Among them, supporters of far-left candidate Jean-Luc Mélenchon, who could sway the results significantly after he narrowly missed out. Mr Mélenchon, who won 19.5 per cent of the vote, has refused to endorse either Ms Le Pen or Mr Macron.

It is not the first time the far-right Front National party got through to the second round of an election. In 2002, Jean-Marie Le Pen faced conservative Jacques Chirac in the final run-off.

At the time, French voters came out en masse against Mr Le Pen, but this year's campaign has seen the “Republican Front”, in which all parties unite against the far right, crumble.

An anti-Le Pen poster in Paris depicts the Front National leader with the face of US President, reading: ‘Do not Trump yourself. Choose France. Vote!’ (Getty)

The final leg of the campaign has also been caught up in security concerns. Less than 48 hours before polling stations opened, there was a huge leak of emails and campaign documents from Mr Macron's campaign team.

France's electoral commission ordered the media not to publish contents of the leaked documents to avoid influencing the election.

Under election rules, Mr Macron or his team were not allowed to comment on any allegations after 10pm on Friday.

In a statement released shortly before the rules came in to force, En Marche! said it had “been the victim of a massive and coordinated hack” and slammed the incident as an attempt to “seed doubt and disinformation” in the minds of voters.

En Marche! previously complained about attempts to hack its emails, blaming Russian groups in part for the cyber attacks amid denials of official involvement from the Kremlin.

Security has been an omnipresent theme of this campaign, which was marked by the death of police officer Xavier Jugelé, killed by a suspected Isis supporter, who opened fire on the Champs-Élysées in Paris three days before the first round of the election.

France has been under a state of emergency since the Paris attacks in November 2015, when 130 people were killed. More than 240 people have died across the country in terror attacks in the past two years.