French presidential candidate Emmanuel Macron addresses a campaign rally in Paris on April 17, 2017. (Yoan Valat/EPA)

The French campaign watchdog on Saturday began investigating the “massive and coordinated piracy action” that presidential candidate Emmanuel Macron reported just minutes before the official end of campaigning in the most heated election for the presidency that France has seen in decades.

Late Friday, the Macron campaign said in a statement that it had been the victim of a major hacking operation that saw thousands of emails and other internal communications dumped into the public domain.

At the end of a high-stakes race, the news quickly stoked fears of a targeted operation meant to destabilize the electoral process, especially after reports of Russian hacking in the U.S. presidential election.

Macron, an independent centrist, is facing off against the far-right populist ­and National Front leader Marine Le Pen, who for years has benefited from considerable Russian financial support and from favorable coverage in state-run Russian media. Voters are set to decide Sunday which candidate becomes France’s next president.

(Sarah Parnass/The Washington Post)

“Intervening in the last hour of the official campaign, this operation is obviously a democratic destabilization, as has already been seen in the United States during the last presidential campaign,” the Macron campaign said.

It was not immediately clear who was being blamed for the hacking, which the campaign said had led to the leaking of documents via social media networks. The campaign could not be reached for further comment late Friday.

The exact contents of the documents were not specified, although the campaign’s statement said real documents — such as emails from personal and professional accounts, contracts and accounting statements — were mixed in with false ones.

“The ambition of the authors of this leak is obviously to harm the movement En Marche! in the final hours before the second round of the French presidential election,” the Macron statement read. En Marche (Onward) is the centrist political movement that Macron founded a year ago with a platform that blends certain aspects of fiscal conservatism with social liberalism.

The campaign immediately filed complaints with France’s National Commission for Campaign Accounts and Political Financing.

Unlike in the United States, campaigning in France comes to a hard stop a day before voters go to the polls. The official end of campaigning was midnight Friday, and candidates may not actively campaign after that time.

(Sarah Parnass,Dani Player/The Washington Post)

The disclosure of the leaked documents just before the end of Friday means the Macron campaign will not be able to address the matter substantially Saturday. Candidates and their aides are strictly prohibited from giving interviews to the press on the day before and the day of the vote.

Despite the prohibition, Macron’s opponents quickly capitalized on the news. Florian Philippot, the National Front’s deputy leader, tweeted early Saturday: “Will #Macronleaks teach us something that investigative journalism has deliberately killed?”

On Saturday, France’s Electoral Commission urged journalists and media organizations not to report on the contents of the leaks. The commission called on news outlets to heed “the sense of responsibility they must demonstrate, as at stake are the free expression of voters and the sincerity of the election” itself.

Throughout the campaign, Le Pen has been an outspoken advocate of pivoting France’s foreign policy toward an improved alliance with Vladimir Putin’s Russia. During a March visit to Moscow, she met with the Russian president.

For years, a complex web of financial ties has also linked Le Pen to Russian lending sources. When French banks refused on principle to lend to the National Front in 2014, Le Pen sought and received the backing of a Russian lender. The bank’s lending license was ultimately revoked late last year, forcing her to seek alternate funding sources.

For months, Le Pen has also received exceedingly positive coverage in Russian state media. Meanwhile, those news outlets have pilloried Macron, accusing him of being secretly gay and of embezzling public funds. To date, most of those rumors seem to have had little effect on French voters.

But the cybersphere has remained a continual source of anxiety for French authorities and voters.

Throughout the campaign, Macron has frequently said that his campaign has been the target of Russian meddling, though the Kremlin has repeatedly denied those accusations. In March, France’s National Cybersecurity Agency said that there was “an extremely high risk” of cyberattacks and hacking of the country’s electoral process, prompting the French government to suspend electronic voting this year for French citizens overseas.

On Wednesday, hours before the beginning of the last televised debate between Macron and Le Pen, various Twitter accounts began spreading rumors that Macron maintained offshore bank accounts. Le Pen then repeated the allegation in the debate, causing Macron to say that she was “subject to the diktats” of the Kremlin.

Polls show Macron, a former investment banker and Socialist finance minister, with a considerable lead over Le Pen, at 63 percent to 37 percent of the vote, according to the latest analyses released late Friday.

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