Sid Ahmed Ghlam was arrested Sunday after he called for an ambulance to treat what appeared to be an accidental self-inflicted gunshot wound to the leg. Police who responded to the scene found weapons in his car and notes indicating potential targets for an “imminent attack", Cazeneuve said.
Authorities then searched his home and discovered an arsenal of Kalashnikov assault rifles, hand guns, ammunition and bullet-proof vests, he said.
Prosecutor Francois Molins told French news agency AFP that documents in Arabic mentioning the Islamic State armed group and Al-Qaeda were found at Ghlam's home.
Meanwhile, police also found DNA evidence linking Ghlam to the death of 32-year-old Aurelie Chatelain, who was found shot dead in her car Sunday in the town of Villejuif just outside Paris.
French Prime Minister Manuel Valls visited two churches in Villejuif Wednesday that were the apparent focus of the attack, which aimed to target "the Christians, the Catholics of France".
"To target a church is to target a symbol of France, the very essence of France," he said to reporters.
The man had been known to police due to comments he had made on social networks, but authorities who had made checks on him in 2014 and 2015 did not find anything to warrant further investigation.
France has been on maximum alert following the January terror attacks on the offices of the Charlie Hebdo satirical weekly and a Jewish food shop, in which 17 people were killed.
Valls stressed that the country continues to face an "unprecedented terrorist threat".
"Terrorists are targeting France to divide us and our response must of course be to protect citizens but also to rally together, unite and to be hugely determined faced with this terrorist threat," Valls said on French television.