Police said Wednesday that they have taken a 24-year-old computer science student into custody in Paris, after he called emergency services to request treatment for a gunshot wound.
An Interior Ministry official said the man was an Algerian national who had stockpiled weapons and bulletproof vests in his apartment, along with documents indicating he was planning attacks on at least one church and possibly more.
They found that he was a radical Islamist, but no evidence that he was connected to a particular terrorist group.
Officials said he called emergency services after accidentally shooting himself.
France has increased security operations since early January, when Islamic militants opened fire on the Paris offices of satirical magazine Charlie Hebdoand began a three-day shooting spree that left 20 people dead.
An Interior Ministry source told Reuters the man was also suspected of being involved in the murder of a 32-year-old woman found dead in her car on Sunday.
Interior Minister Bernard Cazeneuve said the man had previously come to the attention of the French authorities as possibly wanting to go to Syria. Police had made checks on him in 2014 and 2015 without finding anything that would warrant further investigation, Reuters reported.