"The files circulating were obtained several weeks ago due to the hacking of the personal and professional mailboxes of several party officials," Macron's En Marche! (On The Move) party said in a statement, just as campaigning officially ended ahead of Sunday's election.
Macron's team added that all the documents were "lawful".
The online leak came barely 24 hours before Sunday's final round of the presidential election -- one of the country's most dramatic in decades -- in which the centrist former economy minister faces far-right leader Marine Le Pen.
WikiLeaks said there were around 9 gigabytes of data in total, saying it was "checking parts" of the cache.
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