Voting already began on Saturday for French overseas territories and French residents in the United States and Canada, a day before the main first round of presidential elections in France.
France is poised to head to the polls on Sunday under heightened security to elect its new president who lead a country facing multiple challenges including terrorism.
More than 50,000 police officers and soldiers have been fully mobilised for special election duty across the country.
Security was thrust to the fore of the already acrimonious campaign after a policeman was killed by a suspected Daesh member in Paris on Thursday.
French media reported that government security authority DCSP, had circulated a note saying the threat during the elections of a militant attack like the ones that have killed more than 230 people in the past two years in France, was a "constant and pregnant" one.
Voting already began on Saturday for French overseas territories and French residents in the United States and Canada, a day before the main first round of the poll.
The first round will send two of 11 candidates into a run-off vote in two weeks' time to pick a new president for France, a core member of the European Union and the NATO alliance.
TRT World's Myriam Francois reports from Paris.
With two anti-globalisation candidates whose policies could break up the EU among the four front-runners, the vote is of major significance to the international political status quo and to investment markets.
Surveys suggest that nearly a quarter of voters are still undecided and until now, the French have been more concerned about jobs and the economy than terrorism.
But analysts said the policeman's shooting could shift opinions, perhaps handing an advantage to candidates seen as taking a hard line on security, such as far-right leader Marine Le Pen.
Polls make centrist and pro-European Emmanuel Macron the favourite, but he has no established party of his own and is a relatively unknown political quantity.
His three close rivals, according to voting surveys, include the anti-EU, anti-immigration National Front leader Le Pen, who would dump the Euro currency and revive the French Franc.
Far-left candidate Jean-Luc Melenchon wants France to rip up international trade treaties and quit NATO, while conservative Francois Fillon's reputation has been sullied by a nepotism scandal.
TRT World's Simon McGregor-Wood brings more from Paris.
Difficult to pick winner
Although pollsters put Le Pen in second place behind Macron in the first round, she is seen as unlikely to win the second. Melenchon, by contrast, could take the presidency according to some scenarios.
Polls in the dying days of the campaign put all the candidates roughly on between a fifth and a quarter of the vote, with around five percentage points or less separating them -- threatening the margin of error for polling companies.
High levels of abstention and indecision are also a key factor.
However, unlike rest of the France, wealthy residents of Neuilly-sur-Seine seem to have made up their minds about who they will be voting for on Sunday.
TRT World's Anelise Borges spent time in the posh suburb in western Paris.
Voters in the tiny French island of Saint-Pierre and Miquelon, south of Canada's Newfoundland in the north Atlantic, were first to start voting on Saturday morning.
In other US cities and in Canada, voting took place at French consular offices. In Montreal, voters waited for up to three hours in a queue stretching for over 2 km, suggesting a big turnout, French media reported.
Results from ballots cast in the territories and North America will remain sealed until Sunday evening and after polls have closed in mainland France.
Man arrested at Paris station
A knife-wielding man threatened police at Gare du Nord train station in Paris on Saturday, causing panic before he was arrested.
A spokesman for French rail operator SNCF said the man had approached gendarmes patrolling the train station.
He was told to lie down and followed the orders before he was arrested.
The scene led to panic among passengers who tried to flee the scene, a witness said, adding that trains have been delayed.