The campaign of French presidential candidate Emmanuel Macron says it has been the target of a “massive hacking attack” after a trove of documents was released online.
The campaign said that genuine files were mixed up with fake ones in order to confuse people.
It said it was clear that hackers wanted to undermine Mr Macron ahead of Sunday’s second round vote.
The centrist will face off against far-right candidate Marine Le Pen.
The documents were leaked on a file sharing website late on Friday and the Macron camp condemned the action just before the official campaigning period ended at midnight (22:00 GMT).
Candidates and the media now face restrictions until the polls close on Sunday evening, meaning Mr Macron cannot issue further statements.
Opinion polls had indicated the former economy minister carried a lead of 20 percentage points or more over Ms Le Pen.
What was released?
About nine gigabytes of data were posted online by an anonymous user.
Mr Macron’s En Marche movement said internal campaign documents, including emails and financial data, had been taken in an “act of massive, co-ordinated hacking”.
“The leaked files were obtained several weeks ago by hacking personal and professional email accounts of several officials of the movement,” it said in a statement.
The campaign said the documents showed only legitimate campaign activities.
France’s election commission warned that publication or republication of the leaked information could be a criminal offence.
Who might be responsible?
That too remains unclear. The Macron camp has not blamed any specific party but said the hack clearly aimed to damage it and undermine French democracy,
It compared it to the leak of Democratic Party emails in last year’s US presidential election that was blamed on Russian hackers.
Wikileaks, which published those emails, posted a link to the Macron documents on Twitter but implied it was not responsible.
It’s not the first time Macron’s been targeted
Mr Macron’s team has already been the victim of hacking attacks, for which it has blamed groups based in Russia and Ukraine. It suspects the Kremlin of wanting to help Ms Le Pen, who supports a pro-Moscow foreign policy.