In his first reaction to the hacking of Emmanuel Macron's campaign emails, French President Francois Hollande said Saturday the authorities would investigate the incident.

"We knew that there were these risks during the presidential campaign because it happened elsewhere. Nothing will go without a response," Hollande told the AFP news agency during a visit to a cultural institute in Paris.

"If there has been any interference or appropriations, there will be procedures that will begin," said the French president, adding: "We need to let the investigation happen."

Centrist candidate Emmanuel Macron's campaign team said late on Friday it had been the victim of a "massive and coordinated" hacking attack.

The campaign team said in a statement that internal communications and financial documents had been hacked a few weeks ago and were now being circulated across social media at the 11th hour of one of the most dramatic presidential elections in French history. Whoever was behind the leak had sought to "seed doubt and misinformation" a day before Sunday's final run-off vote for the French presidency between the former banker turned economy minister and his anti-immigration rival, Marine Le Pen.

The campaign team also said false documents had been mixed with the leaked campaign files.

"Throughout the campaign, En Marche! has constantly been the party the most targeted by such attempts, in an intense and repeated fashion," the campaign said in a lengthy statement. "The aim of those behind this leak is, all evidence suggests, to hurt the En Marche! party several hours before the second round of the French presidential election."

On Saturday, French officials warned media not to publish hacked material as it could break the law. Election officials asked media to "show a spirit of responsibility and not to relay these contents, in order to not alter the integrity of the vote."

"The dissemination or republishing of such content, obtained fraudulently and in all likelihood possibly altered, could be subject to punishment," they said.

Hacking's possible effect on the vote

Macron's team described the hacking as an attempt at "democratic destabilization," similar to the one during last year's US presidential campaign.

Hollande, however, said he was unable to endorse the view. "I can't say," he said.

The anti-secrecy group WikiLeaks, which posted a link to the trove of leaked documents on Twitter, also questioned the intent of the leak, saying it was likely too late to shift public opinion and affect the outcome of the French election.

In the final pre-election polls - released after Macron scored what many believed to be a knockout blow in Wednesday's televised debate but ahead of the hacking scandal - he led the anti-immigrant Le Pen by about 25 points.

Macron has benefited from broad distaste for the far-right Le Pen, at whom protesters hurled eggs during a recent campaign stop. Nevertheless, 48-year-old Le Pen has brought her National Front party, once a pariah for its racism and anti-Semitism, closer than ever to the French presidency.

Read more: Le Pen's 'outsider' politics move to center stage in France

Many French centrists worry that the published emails could kill any remaining enthusiasm for the 39-year-old Macron, who endorsed "reforms" to gut labor protections during his tenure as economy minister. Only about two-thirds of eligible voters plan to turn out on Sunday.

Fifty thousand police officers, gendarmes and soldiers will be deployed to keep the election day peace across France.

shs/se (AFP, Reuters, dpa, AP)