PARIS - French police have detained a man they suspect of planning an imminent armed attack on one or two churches, the interior minister said on Wednesday.

The man, a 24-year-old information technology student, was arrested on Sunday in southeast Paris. A car was also seized along with handguns, other weapons and bulletproof vests, minister Bernard Cazeneuve said.

France heightened surveillance of potential attackers by its intelligence services and deployed troops to patrol sensitive sites after Islamist militants killed 17 people in January in attacks on the offices of the Charlie Hebdo satirical weekly and a Jewish food shop.

An Interior Ministry source said the man, also suspected of being involved in the murder of a 32-year-old woman found dead in her car on Sunday, was an Algerian national.

"Detailed documents that were also found established beyond doubt that the individual was planning an imminent attack, probably on one or two churches," Cazeneuve said.

He was arrested after calling emergency services to treat a wound, the interior ministry source said. When they arrived, they saw the injury was a gunshot wound and notified police. A blood trail led to a car which contained the weapons.

Police suspect the 24-year-old accidentally shot himself, the source said.

Cazeneuve said he 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.