French President Francois Hollande on Saturday promised a response to the hacking of centrist presidential candidate Emmanuel Macron's campaign following the publication online of thousands of stolen emails and documents.
"We knew that there were these risks during the presidential campaign because it happened elsewhere. Nothing will go without a response," he told AFP during a visit of a cultural institute in Paris.
"If there has been any interference or appropriations, there will be procedures which will begin," he said, adding: "We need to let the investigations happen."
France's electoral commission has warned French journalists not to reveal the contents of the hacked messages on the last day before the election when no campaigning is authorised.
The documents spread on social media just before midnight on Friday in what Macron's team termed an attempt at "democratic destabilisation, like that seen during the last presidential campaign in the United States".
Hollande added that "since we learned that there are these operations, that there are these threats, we have been extremely vigilant."
He said he was unable to say whether it was an attempt at destabilising the election, as alleged by Macron's team.
"I can't say," he said, speaking at the Arab World Institute while accompanied by the king of Morocco, Mohammed VI.