French authorities took a hard line Saturday on what presidential frontrunner Emmanuel Macron called a "massive" hacking attack on his campaign, warning on the eve of the vote that anyone spreading the information could be committing a crime.
The warning came after the pro-Europe centrist's team lambasted a "massive and coordinated" hack that resulted in the online leak of thousands of emails, accounting details and internal documents late Friday.
It was an unexpected 11th-hour twist ahead of Sunday's decisive run-off after a bruising and divisive campaign pitting the 39-year-old former banker who embraces free-trade against his anti-EU, far-right rival Marine Le Pen.
"The dissemination of such data, which have been fraudulently obtained and in all likelihood may have been mingled with false information, is liable to be classified as a criminal offence," France's electoral commission said in a statement.
The documents spread on social media just before midnight as the candidates officially wrapped up campaigning, in what Macron's team termed an attempt at "democratic destabilisation, like that seen during the last presidential campaign in the United States".
Hillary Clinton has alleged Russian hacking of her campaign's emails was partly to blame for her defeat by Donald Trump in the US presidential election in November.
Macron's team said the files were stolen weeks ago when several officials from his En Marche party had their personal and work emails hacked -- in one of "an intense and repeated" series of cyber-attacks targeting Macron since the launch of the campaign.
"Clearly, the documents arising from the hacking are all lawful and show the normal functioning of a presidential campaign," aides said in a statement.
But they warned that whoever was behind the leak had mixed fake documents with real ones "in order to sow doubt and disinformation".
The WikiLeaks website on Friday posted a link to the documents on Twitter, saying it had not yet discovered fakes in the cache of files and "we are very skeptical that the Macron campaign is faster than us."
Last month cybersecurity research group Trend Micro said Russian hackers called Pawn Storm had targeted Macron's campaign, using "phishing" techniques to try and steal personal data.
Senior Le Pen aide Florian Philippot suggested on Twitter that the leak might contain information the media had deliberately suppressed.
The election watchdog advised media not to publish details from the documents, warning that publication could lead to criminal charges and that some of the documents were probably fake.
