The attack has been deemed a "terrorist act" by police.
A teenager has been arrested.
The French government made the move following the shootings in Moscow.
Security agencies are preparing advice over an application to revoke a terrorist designation.
A 19-year-old converted to Islam during the COVID-19 lockdown and then became quickly radicalised by watching extremist material on the internet.
The three individuals tried to obscure who they were online.
They also completed their terrorism control order without police conducting a single search of their home.
"An attack remains a realistic possibility and individuals of concern are still being investigated."
"Knowing more about the threats that we face actually makes people feel more confident in our ability to respond to them."
