French presidential frontrunner, independent centrist Emmanuel Macron, has been the victim of a "massive and coordinated hacking operation", after files purporting to be from the campaign were posted online via social media, reports said.

French presidential frontrunner, independent centrist Emmanuel Macron, has been the victim of a "massive and coordinated hacking operation", after files purporting to be from the campaign were posted online via social media, reports said.

Campaign officials in a statement on Friday said the perpetrators of the hack, revealed less than 48 hours before the final presidential runoff on Sunday against far-right nationalist Marine Le Pen, had mixed fake documents with authentic ones "in order to create confusion and misinformation", CNN reported.

About 14.5 gigabytes of emails, personal and business documents and links to the 70,000-plus files were posted on pastebin, a text-sharing site, just before 2 p.m. on Friday afternoon.

The statement said that by happening near the end of the campaign, the operation is clearly meant to undermine democracy, just like during the US presidential campaign. 

Macron, if successful in Sunday's final vote, would become the youngest President in the history of France and the nation's youngest leader since Napoleon.

His political organisation, En Marche, called the attack the latest in a series of cyber intrusions.

"The files that are circulated were obtained several weeks ago following the hacking of personal and professional mail boxes," CNN quoted En Marche as saying.

According to experts, Macront has led a remarkable campaign, defying the traditional mainstream parties courtesy of his En Marche movement. 

Macron has been endorsed by President Francois Hollande, Republican candidate Francois Fillon and the Socialist Party's Benoit Hamon, along with former US President Barack Obama.

Five new opinion polls published on Friday forecast that Macron would win the election with a share of 62-63 per cent, comfortably defeating Le Pen, reports The Guardian.

He still holds a 20 per cent lead.

Macron's team has previously blamed Russian interests for repeated attempts to hack its systems during the campaign, saying that it had been the target of unsuccessful attempts to steal email credentials since January. 

Russia has denied any involvement.

The outcome of Sunday's runoff will be clear the same day. The results will be officially proclaimed by France's constitutional council on May 11, reports the BBC.

May 14 marks the end of outgoing President François Hollande's term, and is the latest possible date for the inauguration and official transfer of power to his successor.