At the inauguration of a new Olympic swimming centre, reporters asked if he thought Russia was targeting the Games.
“Without a doubt,” he said, “including in the field of information.
“Every day (Russia) is putting out stories saying that we are unable to do this or that, so (the Games) would be at risk.”
The French government says Russia has recently stepped up propaganda attacks on France, using fake accounts on social media to spread rumours and disinformation.
It follows Mr Macron’s switch to a more hard-line policy on the Ukraine war, to which he no longer refuses to rule out eventually sending French troops on the side of Kyiv.
France believes Russian intelligence was behind the daubing of Israeli Stars of David on Paris walls after the October 7 Hamas attacks, in what was interpreted as a bid to stir up divisions in France.
A network of Russian-created websites named Portal Kombat is accused of spreading made-up stories, such as claims that French mercenaries are already serving in Ukraine, or that Mr Macron cancelled a trip to Kyiv because of fears of an assassination attempt.
After the Crocus City Hall terrorist attack near Moscow, the French and Russian defence ministers had a rare telephone exchange on Wednesday.
According to Mr Macron, this was because France had intelligence information that could help the Russians know more about the alleged attackers, from the Afghan section of the Islamic State group.
In his account of their conversation, French Defence Minister Sebastien Lecornu said he told his counterpart Sergei Shoigu that France was concerned about Russian claims that Kyiv was behind the Crocus City Hall attack – claims for which France said there was no evidence.
But in his account of the phone call, Mr Shoigu said: “The Kyiv regime does nothing without the approval of its western minders. We hope that in the case (of the Crocus City Hall attack) the French secret services are not involved.”
Asked about Mr Shoigu’s remarks on Thursday, Mr Macron said they were “bizarre and menacing … ridiculous.”
The president confirmed for the first time that there are alternative plans for the Olympics opening ceremony in July, if the terrorist threat worsens.
Currently the 26 July ceremony is supposed to take place on boats in the river Seine, with more than 300,000 people watching from the quays. However experts have warned that the occasion is highly vulnerable to terrorist attack.
“We will be ready,” Mr Macron said. “We are preparing several scenarios. If the threat were to evolve, if we considered that circumstances made it necessary, we have back-up scenarios.”
Mr Macron also lent his support to the popular French-Malian singer Aya Nakamura, whose name has been mentioned as a possible performer at the opening ceremony. Critics on the hard-right of French politics say she would not be a good ambassador because the language of her songs is often crude and difficult to understand.
“She speaks to a good number of our fellow citizens and I believe she has every right to be at the opening or closing ceremonies of the Games,” the president said.