A huge leak of emails from Emmanuel Macron’s campaign team may have been orchestrated by the same group behind the Democratic National Committee leak, analysts say.

Code within a cache of up to 9GB of data and documents posted on an anonymous filesharing website was partly written in Russian, despite apparent efforts to delete metadata.

Vitali Kremez, director of research with US-based cyber intelligence firm Flashpoint, said his analysis indicated that APT 28, a group tied to Russia’s GRU military intelligence directorate, was behind the leak.

The collective, also known as “Fancy Bear” and “Sofacy”, has been linked to cyber attacks on the Democratic National Committee during the US election, the White House, German Parliament, Nato and French media.

Last month, APT 28 hackers registered decoy internet addresses to mimic the name of Mr Macron’s En Marche! party.

Attackers are believed to have used the domains to send corrupted emails to hack into the campaign’s computers, Mr Kremez said.

“If indeed driven by Moscow, this leak appears to be a significant escalation over the previous Russian operations aimed at the US presidential election, expanding the approach and scope of effort from simple espionage efforts towards more direct attempts to sway the outcome,” he added.

The leak came just little over a day before Mr Macron faces Marine Le Pen in the second and decisive vote of the French presidential election, where he has enjoyed a comfortable lead in polls.

It emerged on 4chan, where an anonymous poster provided links to documents on Pastebin with the message: “This was passed on to me today so now I am giving it to you, the people.”

Mr Macron’s En Marche! party confirmed it had “been the victim of a massive and coordinated hack” on Friday evening, adding that it had “given rise to the diffusion on social media of various internal information”.

A spokesperson said the communications only showed the normal functioning of a presidential campaign, but that authentic documents had been mixed on social media with fakes to sow “doubt and misinformation”.

Far-right American activists are believed to be behind early efforts to spread the documents on social media, before they were picked up by Ms Le Pen’s supporters in France.

The hashtag #MacronLeaks was spread by prominent Twitter accounts including that of Jack Posobiec, a pro-Donald Trump activist and employee of the far-right site Rebel TV.

France’s electoral commission warned local media that they could face prosecution for reporting on the content of the leaks, under rules that came into force at midnight to prevent influence on the election.

Ben Nimmo, of the Atlantic Council’s Digital Forensic Research Lab, said the mass document drop appeared to have been deliberately timed just hours before restrictions kicked in.

He said that the contents appeared to be “99 per cent boring” but that a social media frenzy over alleged “censorship” distracted from a lack of explosive revelations.

“The timing is interesting because it’s really targeted at that purdah period where the campaign can’t say anything and the mainstream media can’t do much,” he told The Independent.

Barack Obama backs Emmanuel Macron for French president in video message

“The fact it was dropped so close to the bell does mean that it’s very hard for anyone to dissect it, to verify it, to push back on it – but you’re also limiting its potential spread, so it goes both ways.”

Mr Nimmo has been monitoring a “very vocal and very aggressive” social media campaign supporting Ms Le Pen leading up to the election.

He said it has been aided by the alt-right in the US and UK, which has been launching its own “meme war” against the Front National leader’s rivals.

Because most of the images created being in English rather than French, the impact had so far been limited, Mr Nimmo said, but there are a number of automated “bots” on Twitter churning out anti-Macron stories and slogans.

He said the En Marche! leaks and other conspiracy theories targeting Mr Macron had exposed a “real confluence of interest” between Russia and the far right in Russia and France.

“They’re not necessarily coordinated, but they’re interested in a lot of the same stuff,” Mr Nimmo added.

“The most active accounts tweeting on the leaks support Ms Le Pen anyway, so that won’t solve her problem attracting new voters.

“I have not seen anything yet to suggest that the alt-right will be able to overturn a 20-point deficit in the polls.”

French Presidential Election Show all 20 1 /20 French Presidential Election French Presidential Election Voters line up to cast their ballots REUTERS French Presidential Election French expats queue along the street outside the Lycee Francais Charles de Gaulle to cast their vote in a polling station inside the school, in the first round of the 2017 French presidential election, in London, Britain April 23, 2017. REUTERS/Luke MacGregor - RTS13JM5 REUTERS French Presidential Election People line up to vote in the first round of 2017 French presidential election at a polling station in Vaulx-en-Velin near Lyon, France, April 23, 2017. REUTERS/Emmanuel Foudrot - RTS13HSP REUTERS French Presidential Election Police patrol polling stations in France REUTERS French Presidential Election Francois Fillon (L), member of the Republicans political party and 2017 French presidential election candidate of the French centre-right, casts his vote in the first round of 2017 French presidential election in Paris, France, April 23, 2017. REUTERS/Christophe Archambault/Pool - RTS13IH0 REUTERS French Presidential Election Benoit Hamon (C), French Socialist party 2017 presidential candidate, is surrounded by photographers as he leaves a polling station after voting in the first round of 2017 French presidential election in Trappes, near Paris, France, April 23, 2017. REUTERS/Vincent Kessler - RTS13I0Y REUTERS French Presidential Election French President Francois Hollande collects voting slips before casting his ballot in the first round of the 2017 French presidential election at a polling station in Tulle, France, on April 23, 2017. REUTERS/Georges Gobet/Pool - RTS13ITO REUTERS French Presidential Election A policeman walks by election posters near a polling station during the first round of 2017 French presidential election in Paris, France, April 23, 2017. REUTERS/Christian Hartmann - RTS13I3A REUTERS French Presidential Election Emmanuel Macron and wife Brigitte Trogneux REUTERS French Presidential Election Emmanuel Macron casts his ballot REUTERS French Presidential Election Emmanuel Macron, head of the political movement En Marche !, or Onwards !, and candidate for the 2017 French presidential election, waves hand during in the first round of 2017 French presidential election at a polling station in Le Touquet, northern France, April 23, 2017. REUTERS/Benoit Tessier - RTS13ICH SAA/ French Presidential Election Jean-Luc Melenchon, candidate of the French far-left Parti de Gauche and candidate for the French 2017 presidential election, leaves a polling booth in the first round of 2017 French presidential election at a polling station in Paris, France, April 23, 2017. REUTERS/Stephane Mahe - RTS13IKB REUTERS French Presidential Election Front National leader Marine Le Pen casts her ballot Marine Le Pen (L), French National Front (FN) political party leader and candidate for French 2017 presidential election, casts her ballot in the first round of 2017 French presidential election at a polling station in Henin-Beaumont, northern France, April 23, 2017. At R, Mayor of Henin-Beaumont Steeve Briois. REUTERS/Charles Platiau - RTS13IEI REUTERS French Presidential Election Early ballots are read as results continue to come in Reuters French Presidential Election Macron supporters react as results come in early in the evening AP French Presidential Election Supporters of Front National leader Marine Le Pen cheer as early results come in Reuters French Presidential Election Alamy Live News. J21KYW Paris, France. 23rd April 2017. Marcon supporters wave French and EU flags after the announcement that he is the leader in the exit polls after the polling stations have been closed. Supporters of Emmanuel Macron, the Presidential candidate from the social liberal political party En Marche! celebrate the exit polls, that see him in first place, ahead of Marine Le Pen from the Front National in the first round of the French Presidential election. Credit: Michael Debets/Alamy Live News This is an Alamy Live News image and may not be part of your current Alamy deal . If you are unsure, please contact our sales team to check. Alamy French Presidential Election Front National leader Marine Le Pen takes to the stage to address her supporters as fans cheer Reuters French Presidential Election Emmanuel Macron greets supporters on Sunday night AP French Presidential Election Emmanuel Macron and wife Brigitte Trogneux celebrate the incoming results EPA

As the #MacronLeaks hashtag buzzed around social media, Florian Philippot, deputy leader of the Front National, tweeted: “Will #MacronLeaks teach us something that investigative journalism has deliberately kept silent?”

French media was attempting to cover the leak without violating election restrictions, with Le Monde publishing a statement saying it would not publish the content before the election.

The newspaper said the huge amount of data meant there was not enough time to report on it properly and claimed the dossiers had been published on purpose 48 hours before the election with the clear aim of "disrupting the political process".

“If these documents contain revelations, Le Monde will of course publish them after having investigated them, respecting our journalistic and ethical rules, and without allowing ourselves to be exploited by the publishing calendar of anonymous actors,” it said.

The cyber attack came just 10 days after the En Marche! digital chief Mounir Mahjoubi said it had been targeted by Russia-linked hackers – but that those hacking attempts had all been thwarted.

Officials reported failed attempts to steal email credentials dating back to January, identifying a hacking group operating in Ukraine.

There have been repeated allegations of Russian interference in elections across Europe and the US, with Mr Macron previously targeting state media for spreading “fake news” to damage his campaign.

Mr Macron has launched a legal complaint over allegations of an offshore bank account, which has triggered an inquiry into the suspected spread of false stories aimed at influencing the election.