French voters are casting their ballots in what will most probably be the first of a two-round election to choose a new president.

The first round of the election on Sunday will be a closely fought contest, particularly between four of the 11 candidates in the race.

The four leading candidates are: Emmanuel Macron, a former minister and leader of the centrist En Marche! party; Marine Le Pen, president of the far-right National Front; Francois Fillon, a former minister and leader of the conservative Republican party; and Jean-Luc Melenchon, leader of the far-left La France Insoumise party.

The fact that there are 11 candidates may prevent a decisive victory, with many analysts predicting that a vote of more than 50 percent, required for an outright win, is unlikely to be achieved by any of the leading contenders.

In the event that no candidate secures an absolute majority, a second round of voting - pitting the two top candidates against each other - will take place on May 7.

All projections stipulate a run-off between the 48-year-old leader of France's far-right National Front (FN) Marine Le Pen and the young centrist independent candidate Emmanuel Macron, 39.

But the battle will not be easy, as both conservative party candidate Francois Fillon and leader of the far left Jean-Luc Melenchon are  projected to do well in the first round.

Polling stations will close at 17:00 GMT; projected results are expected shortly afterwards.

Opinion polls ahead of the vote said 50 percent of the 47 million voters remain undecided on their vote. Thirty percent who planned to abstain were expected to help set a record low turnout.

Pollsters say a low turnout favours Le Pen, whose supporters are the most determined to vote.

However, by midday Sunday at least 28.54 percent of eligible voters had cast their ballot compared with 28.29 percent in 2012 - meaning turnout was high.

This year's election was marred by a shooting incident in central Paris, after an attacker opened fire on a police van on the Champs Elysees on Thursday night, killing one officer and seriously wounding two others.

READ MORE - French Election 2017: Who I'll vote for

It also comes within a year of the unexpected Brexit vote in the UK and the election of populist Donald Trump as president of the United States last November.

In France, the possibilities are no less dramatic with the steady advance of the far-right National Front's Marine Le Pen.

Who will win?

According to pollsters, Le Pen, an anti-European Union candidate, is expected to reach the second round but ultimately lose to Emmanuel Macron.

A Le Pen victory would send shockwaves every bit as seismic as events in the UK and US, probably spelling the end of the EU in its current form.

Her victory would also test the country's already strained relations with its sizeable Muslim community. 

‘Frexit’ concerns ahead of French election

Macron, Le Pen's main challenger and favourite to win, has campaigned on a pro-EU, pro-status quo, centrist outlook, hoping to secure support from those weary of the disruption an unknown quantity, such as Le Pen, may bring.

But Le Pen is not alone in promising major change.

Along with the conservative Francois Fillon, who is 63, the leftist Jean-Luc Melenchon, 65, favours a rapprochement with a Russian government increasingly at odds with the Western order.

Like Le Pen, Melenchon is a Eurosceptic who has promised a referendum on the country's continued membership of the bloc.

While pro-EU, Benoit Hamon, the 49-year-old Socialist Party candidate, is no less radical. He has promised the eventual introduction of a basic income for all French citizens.

The other six candidates include a leftist economics teacher, an anti-American nationalist convinced that the EU is a CIA-backed plot, and a conspiracy theorist who has before called for a "thermonuclear corridor" between Earth and Mars.

None of them is expected to win more than 5 percent of the vote.

Will security concerns affect France's elections?

Source: Al Jazeera News