French authorities say they have foiled a jihadist plot to attack a church after an Algerian who accidentally shot himself was found with a stash of weapons and documents mentioning Islamist militant groups.

The 24-year-old IT student Sid Ahmed Ghlam's plans were exposed purely by chance after he called an ambulance saying he had been shot during an armed robbery at his Paris home, prosecutor Francois Molins told journalists.

However, police uncovered an arsenal of weapons in his car and home, and detailed plans to attack one of two churches, as well as DNA evidence linking him to the murder of a woman who was found shot dead in her car over the weekend near the capital.

The suspect, who was admitted to a Paris hospital after his arrest, was known to intelligence services over comments on social networks expressing his desire to go and fight in Syria alongside jihadists, said Interior Minister Bernard Cazeneuve.

Police called to the scene where Ghlam was wounded found traces of his blood in the car as well as a Kalashnikov rifle, handguns, bulletproof vests, several mobile phones, a laptop and documents on "potential targets and how to carry out attacks," said Molins.

Another three Kalashnikovs, police armbands and vests, and documents in Arabic mentioning jihadist groups including Islamic State were found at his home.

The city prosecutor said that Ghlam had told police "far-fetched" tales of how he had received the bullet wound to his leg, such as that he had shot himself while trying to throw his weapons into the Seine river.

Analysis of his communications equipment indicated Ghlam "was in touch with another person who could be in Syria on how to carry out an attack, with the latter clearly asking him to target a church", said Molins.