By Gabriel Stargardter and Raphael Sater

PARIS, May 13 (Reuters) - French authorities are investigating whether an obscure Israeli firm called Blackcor was involved, at least in part, in a foreign interference campaign targeting a far-left party ahead of municipal elections in March, three sources familiar with the matter said.

Two sources said that French intelligence services are currently investigating who may have commissioned Blackcore to carry out the alleged smear campaign against three candidates from the La France Insoumise party, a campaign that included misleading websites and social media accounts alleging criminal behavior, as well as the posting of offensive digital advertisements.

Reuters was unable to independently identify the entity behind Blackcore, verify its headquarters, or find any reference to it in Israeli corporate records.

Blackcore did not respond to repeated messages sent via the contact form on its website and its LinkedIn page, both of which were later shut down.

French prosecutors did not respond to requests for comment or declined to comment on the activities attributed to Blackcore. Vigenom, the disinformation agency of the French prime minister's office, also declined to comment.

Blackcore describes itself on its website and LinkedIn page as "an elite influence, cyberspace and technology company, created for the modern age of information warfare."

She said it provides governments and political campaigns with "sophisticated strategies, advanced tools, and robust security systems for shaping narratives."

Reuters examined Blackcore documents in which the company acknowledged its responsibility for a separate social media operation carried out on behalf of an African government.

The documents were undated, but they indicated a process that began in January of this year and lasted for 14 weeks. A person provided the documents to Reuters but requested that some details be withheld.

After Reuters asked Meta Platforms, Facebook's parent company, about the African operation described in the documents, the company said the "network" behind it was linked to a disinformation campaign launched before the French municipal elections. Meta stopped short of identifying the entity responsible.

Meta told Reuters that it had removed a network of accounts and pages for violating its rules against "coordinated inauthentic behavior." It said the illicit activity originated in Israel and "primarily targeted France."

Two sources familiar with the disinformation campaign attributed to Blackcore in France said they were also aware of the company's work in Africa, without elaborating.

Two other sources stated that Google and TikTok independently detected aspects of the disinformation campaign in France during monitoring and security operations on their networks. Neither provided further details.

Alphabet-owned Google did not respond to messages requesting comment.

TikTok did not directly address questions regarding Blackcore, but said it had removed an account that Reuters identified as promoting one of the fake websites used in a suspected disinformation campaign against France. TikTok said the account violated its rules against inauthentic behavior.

* The France Unbowed party sparks division of opinion

French authorities and the candidates themselves say the operation targeted Sebastien Delluguet, a candidate for mayor of Marseille, François Bekimal, a candidate in Toulouse, and David Giraud, a candidate in Roubaix.

Le Monde first revealed the focus of this operation in March, when the agency Phygenom uncovered a "limited-range" foreign digital interference scheme targeting a "French political party" and its candidates in Marseille, Toulouse and Roubaix.

The satirical and investigative newspaper Le Canard Enchaîné later reported that authorities suspected an Israeli company, but did not name it.

The suspected disinformation campaign by Blackcore highlights the heightened tension leading up to local elections, at a time when France and other countries are grappling with increasing political polarization and threats to democracy.

Opinion polls show that the France Unbowed party is causing a split in opinions.

The pro-Palestinian party is constantly accused of anti-Semitism by some Jewish community leaders and its political opponents, which the party denies, while a number of businessmen are concerned about its policies involving high taxes and excessive spending.

However, the party still enjoys a strong support base ranging from 10 percent to 15 percent, which analysts say may be enough to reach the second round of the next French presidential election, scheduled for April 2027.

With opinion polls predicting that the far-right National Rally party will reach the second round, centrist French voters fear a possible runoff between the far right and the hard left.

The France Unbowed party said that the Figenom agency had alerted it to foreign interference targeting its candidates, and announced that it was cooperating with investigators.

"We expect the upcoming (presidential) elections to witness attacks of this kind," the party said in a statement.

He added, "Technological advancements are likely to significantly increase this risk."

The Israeli Foreign Ministry told Reuters it was unaware of the existence of Blackcore. It did not comment on whether the French government had contacted it regarding the alleged election interference.

The French Foreign Ministry did not respond to requests for comment.