France's anti-terror police PNAT said a second 18-year-old man had been arrested on Thursday in connection with plans to commit one or several attacks against people.
It did not mention a link to the Olympic Games, which start in Paris on July 26, but France is on its highest state of alert as it gears up to host millions of visitors, athletes and world leaders during the event.
The suspect, who was arrested in an undisclosed holiday location, was in contact -- both in person and through social media networks -- with another 18-year-old man arrested on Tuesday in southwest France, PNAT said.
"Investigations focus on one or several violent actions these young people were considering. At this stage we are trying to assess the reality of their plans beyond discussions conducted online," it said.
On Tuesday, French police arrested a Russian man suspected of planning to destabilise the Olympics, the Paris prosecutor's office said on Wednesday, just days before the Games begin.
The 40-year-old man was detained on Tuesday after police raided his house at the request of the Interior Ministry, the prosecutor's office said in a statement.
The Olympics kick off on Friday with a spectacular but logistically fraught opening ceremony along the River Seine.
France has rolled out its biggest ever security operation to safeguard the Games, which take place against a backdrop of wars in Ukraine and Gaza.
