An Islamic extremist with an arsenal of heavy weapons planned an imminent attack on one or more French churches, France's top security official said Wednesday, announcing the arrest of the man who is also accused in the death of a young woman.

The 24-year-old computer science student was flagged as a risk by security officials last year and earlier this year but there was no specific reason to open a judicial investigation, said Interior Minister Bernard Cazeneuve.

A French security official, who was not authorized to publicly release details, said the suspect — an Algerian who had lived in France for several years — was arrested Sunday after he apparently shot himself by accident and called for an ambulance. Police who arrived at the scene found a blood trail leading to his car, with loaded guns and notes about potential targets inside.

"Documents were also found and they prove, without any ambiguity, that the individual was preparing an imminent attack, in all probability, against one or two churches," Cazeneuve said.

In the man's apartment, in southeastern Paris, more weapons were found as well as Islamic extremist material, the official said. There was no immediate evidence that the suspect had direct ties to any organized groups, the official said.

Aurelie Chatelain, a 32-year-old Frenchwoman visiting Paris for a training session for her work, was found shot to death on Sunday morning in her car. The security official said Chatelain appeared to have been killed by the suspect at random.

France has been on edge since the Jan. 7-9 attacks on the satirical newspaper Charlie Hebdo and a kosher supermarket left 20 people dead, including the three gunmen. In that case, at least two of the gunmen had been flagged to French intelligence — and the third had been recently released from prison after serving a sentence involving his ties to Islamic extremists — but surveillance was called off months before the attack.