The campaign of the French presidential candidate Emmanuel Macron has been targeted by what appear to be the same Russian operatives responsible for hacks of Democratic campaign officials before last year’s American presidential election, a cybersecurity firm warns in a new report.

The report has heightened concerns that Russia may turn its playbook on France in an effort to harm Mr. Macron’s candidacy and bolster that of Mr. Macron’s rival, the National Front leader Marine Le Pen, in the final weeks of the French presidential campaign.

Security researchers at the cybersecurity firm, Trend Micro, said that on March 15 they spotted a hacking group they believe to be a Russian intelligence unit turn its weapons on Mr. Macron’s campaign — sending emails to campaign officials and others with links to fake websites designed to bait them into turning over passwords.

The group began registering several decoy internet addresses last month and as recently as April 15, naming one onedrive-en-marche.fr and another mail-en-marche.fr to mimic the name of Mr. Macron’s political party, En Marche.