French security forces arrested a man suspected of planning an attack during the Olympic torch relay through the western city of Bordeaux, Interior Minister Gérald Darmanin said.
The local public prosecutor's office, however, said that the man had not yet chosen a site for his attack and had not mentioned Thursday's torch relay.
Investigators confiscated a weapon that could fire rubber bullets.
The prosecutors said the suspect had shown interest in the violent and misogynistic "incel" movement, which is characterized by heterosexual men who blame women for their failings in life, romantic or otherwise.
The relatives of the man in his mid-20s stated that he was mentally unstable.
Investigators became aware of the man because of a post about a killing spree 10 years ago in California, in which a student killed six people out of hatred of women. He was taken into custody on Tuesday.
The public prosecutor's office recommended initiating a preliminary investigation into the glorification of a criminal offence and criminal association.
The Olympic flame arrived in the southern French city of Marseilles earlier this month. From there it began its trek across the country - usually via runners, but also other forms of transport - ahead of the 2024 Paris Games that start on July 26.