PARIS -- France's election campaign commission says "a significant amount of data" has been leaked on social networks following a hacking attack allegedly suffered by centrist presidential candidate Emmanuel Macron, 36 hours before the nation votes Sunday in the crucial runoff against Marine Le Pen.

The commission said Saturday that leaked data apparently came from Macron's "information systems and mail accounts from some of his campaign managers." In a statement released after a morning meeting, the watchdog said the leaked data had been "fraudulently" obtained and that fake news has probably been mingled with it.

The commission urged French media and citizens "not to relay" the leaked documents "in order not to alter the sincerity of the vote."

The timing of the leak is very strange, coming at a time when all campaigning has officially stopped and all reporting on the election is likewise supposed to have ceased, CBS News correspondent Mark Phillips reports. The blackout is supposed to be a period of reflection for voters.

Macron's political movement said the unidentified hackers accessed staffers' personal and professional emails and leaked campaign finance material and contracts -- as well as fake decoy documents -- online.

Links from Wikileaks showed lists of documents, but whatever is in them may have limited -- if any -- influence on the election results because of the official news blackout.

The Macron campaign was clearly furious. Slamming the hack as an effort to "seed doubt and disinformation" and destabilize the vote, Macron's movement En Marche said it would "take all measures" to shed light on what happened. It recalled similar leaks from Hillary Clinton's U.S. presidential campaign, which also said that authentic documents were mixed with false ones.

Suspicion for the attack is falling on the Russians and is considered a possible attempt to benefit the faltering campaign of Marine Le Pen, who was jeered out of one of her own rallies Friday. Le Pen -- the right wing, anti-immigration candidate -- is known to be less hostile to the Kremlin and even met with Vladimir Putin during the campaign. She has also received campaign funding from a Russian bank.

The No. 2 in Le Pen's anti-immigration National Front party, Florian Philippot, asked in a tweet, "will the #Macronleaks teach us something that investigative journalism deliberately buried?"

A Le Pen victory in Sunday's election would be a massive surprise, given Macron's 20-point lead in the polls.

Still, with neither of the two remaining two candidates coming from the established political parties, this election has already produced a surprise.