PARIS—In the wake of alleged Russian interference in the U.S. presidential election, a front-runner in France’s presidential race is accusing Moscow of doing it again.

The campaign of candidate Emmanuel Macron said Tuesday in an email to supporters that the Russian government is trying to destabilize his candidacy by using state-funded media outlets to spread smears about his character.

Mr. Macron’s political party En Marche, or On the Move, has also been the target of about 4,000 attempts over the last month to disable or break into its computer servers, many from an unidentified hacker group partly using computer systems in Ukraine, said Mounir Mahjoubi, the campaign’s digital director.

The accusations raise the specter of Moscow persisting with what American and European officials describe as an effort to delegitimize Western democracies and alliances through hacking and misinformation. U.S. intelligence agencies say Kremlin-backed hackers breached email accounts of Democratic Party officials and leaked their contents in an effort to tilt the election for President Donald Trump.

The threat of Russian interference has French security services on high alert, said an official in the French president’s office. The services regularly detect cyberattacks directed at France that are suspected of coming from Russia, but they have yet to uncover evidence of attacks ordered by the Kremlin, according to the official.

“It’s a threat we’re taking seriously,” the official said.


The Kremlin on Tuesday rejected the Macron campaign’s allegations, much as it has denied involvement in hacking during the U.S. election. “Any allegations of official Moscow possibly having anything to do with them [hacking] are absurd,” Kremlin spokesman Dmitry Peskov told Russian news agencies Tuesday.

Most worrying for Mr. Macron’s campaign was an article published Feb. 4 on Sputnik, a news agency funded by the Russian government, claiming the candidate has a “very wealthy gay lobby behind him” and that “controversial details of his personal life” would soon become public.

Sputnik, which is controlled by the Russian state, denied spreading false information. “Sputnik always covers events as they are,” a spokeswoman for the agency said. “While some may find it disturbing, these are facts and leaving them without attention would constitute a violation of the fundamental principle of the freedom of speech.”

Sputnik has also run some stories critical of Mr. Macron’s top rivals, Marine Le Pen of the anti-immigrant National Front and François Fillon of the conservative Les Républicains party.


But analysts say Moscow has more incentive to interfere with Mr. Macron.

“Macron is the candidate who doesn’t have support from Russia, for very simple reasons,” said Thomas Gomart, president of the French Institute of International Relations. “He is pro-Europe, pro-German, and he believes that the euro is a good thing.”

Ms. Le Pen has vowed to pull France out of the North Atlantic Treaty Organization and the European Union, alliances Mr. Putin sees as threats to the Russian sphere of influence. Mr. Fillon has also pledged to mend relations with Moscow. Both he and Ms. Le Pen oppose existing EU sanctions on Russia for the annexation of Crimea and its support of rebels in eastern Ukraine.

On Tuesday an Opinionway poll showed Mr. Macron garnering 22% of the first-round vote in April, second behind Ms. Le Pen with 27%. If the two went to the second-round runoff, the polls said, Mr. Macron would beat Ms. Le Pen 64% to 36%.


Sputnik’s report constitutes “an extremely dangerous threat,” said Mr. Mahjoubi, the digital campaign director. Some French newspapers interpreted the agency’s article—based on an interview with a conservative French lawmaker—as an attempt to bolster a rumor making the rounds: That the candidate, who is married to a woman, was having an affair with the male chief executive of Radio France.

On Feb. 6, Mr. Macron addressed the rumor, joking that any affair would have to be with his hologram, because “that couldn’t be me.”

France’s National Agency for the Security of Information Systems, which is charged with protecting government entities and essential infrastructure from cyberattacks, said it briefed political parties in late October about the hacking threat, advising them to hire private security firms. Mr. Macron’s team met with the agency in January for a similar briefing.

A spokeswoman for ANSSI said the agency has no active role in protecting electoral campaigns, because they are private organizations.


—Olga Razumovskaya in Moscow contributed to this article.

Write to Sam Schechner at sam.schechner@wsj.com and Matthew Dalton at Matthew.Dalton@wsj.com