PARIS-French authorities have filed preliminary charges against two people of plotting an attack days before a tense presidential election. The gunman carried a note praising the Islamic State group.
In the rainy United States capital Washington, voters cast their ballots in the election's first round at a polling station at the French embassy.
The pair now face a run-off vote on 7 May.
"An extra guard or reinforcement of staff will be provided to any polling station that needs it", Paris town hall official Colombe Brossel said.
Concerned about security, the government has mobilized more than 50,000 police and gendarmes to protect 70,000 polling stations, with an additional 7,000 soldiers on patrol.
Polls opened in France's far-flung overseas territories but won't start until Sunday on the French mainland.
The mad-dash campaigning of the last few weeks came to a premature end Friday, hours after a gunman killed a police officer on the famed Champs-Elysees.
Others, fearful that Ms Le Pen has been strengthened by the instability, said they would shift their votes from fringe candidates to make sure they keep the far-right out of power.
There are four leading candidates in a race that is still too close to call.
She has promised a "Frexit" if elected, pledging to "recover the monetary, economic, legislative and territorial sovereignty" of France, re-establish national borders, and leave the Schengen area of free circulation.
Almost 47 million voters will decide, under tight security, whether to back a pro-EU centrist newcomer, a scandal-ridden veteran conservative who wants to slash public spending, a far-left euroskeptic admirer of Fidel Castro or appoint France's first woman president who would shut borders and ditch the euro.More news: Possible shutdown, health care quagmire awaiting Congress
"Some haven't taken the full measure of the evil", 63-year-old Fillon said, promising an "iron-fisted" approach.
François Fillon, a former prime minister of France, also remains in the race despite a scandal surrounding his British-born wife.
Well-wishers paid their respects on Saturday at the site of the shooting, which was adorned with flowers, candles and messages of solidarity for the slain police officer, Xavier Jugele.
Veteran left-winger Melenchon, 65, was the only one of the four to stick to his schedule.
"Several Europes are possible, it doesn't have to be just their Europe", said Melenchon, a eurosceptic who has pledged to renegotiate treaties with the bloc. "Five years until the next French presidential election, in which voters will want to see a proof of why the European Union is a better alternative to a national state", he noted.
A serial offender, he spent almost 14 years in prison for a range of crimes including attacks on the police.
With a broad smile, Le Pen stood before an adoring crowd, said her National Front party will represent "the great alternative" to the French people and pledged to open a "much-needed" debate on globalization.
Le Pen and Fillon canceled their last campaign events Friday over security concerns.
Both US President Donald Trump and his predecessor Barack Obama have shown interest in the vote. So, how do the French decide on a leader?
"I was disappointed by so much lack of transparency and ethics during the campaign", she said. "At worst, I'll cast a blank vote".