France's prime minister says five attacks have been thwarted in France since a January assault by Islamic extremist gunmen left 20 people dead, including the attackers.

Manuel Valls told France Inter radio on Thursday that the five included the planned attack officials said was thwarted Sunday when the would-be gunman apparently shot himself in the leg by accident and called for an ambulance, raising the suspicion of the police.

"The threat has never been so significant," Valls said.

Authorities say the 24-year-old Algerianarrested in Paris on Sunday was targeting one or more churches and was linked to the shooting death of a young woman. The computer science student had been flagged as a security risk this year and in 2014, but managed to amass an arsenal of weapons.