Security forces prevented an attack on French military installations this week by arresting four people whose leader had links to jailed jihadists, Interior Minister Bernard Cazeneuve said on Wednesday.
According to a source close to the situation, the attackers planned to act in January 2016 and were targeting a senior military official in the south of France.
The four were aged between 16 and 23 and arrested in different places around France, the minister said. One was ex-military, he added.
The announcement came as France is on high alert after 17 people were killed in attacks in and around Paris in January.
Last month, a suspected Islamist beheaded his boss and tried to blow up a U.S-owned industrial gas plant in the suburbs of Lyon.
French authorities also confirmed that two fires that broke out at a petrochemical facility near Marseille on Tuesday were started deliberately.