A suspect was arrested on Saturday after an attacker with a sawn-off shotgun shot a Greek Orthodox priest in the chest before fleeing in the French city of Lyon, the prosecutor said.
"A person who could correspond to the description given by the initial witnesses has been placed in policy custody," Lyon's public prosecutor Nicolas Jacquet said in a statement, adding that the suspect had not been carrying a weapon when he was arrested.
The priest was fired on twice at around 4 p.m. (1400 GMT) as he was closing the church, and was being treated on site for life-threatening injuries, the source said.
Witnesses said the church was Greek Orthodox. Another police source said the priest was of Greek nationality, and had been able to tell emergency services as they arrived that he had not recognized his assailant.
The incident came two days after a man shouting "Allahu Akbar!" (God is Greatest) beheaded a woman and killed two other people in a church in Nice. Two weeks ago, a schoolteacher in a Paris suburb was beheaded by an 18-year-old attacker who was apparently incensed by the teacher showing a cartoon of the Prophet Mohammad during a class.
While the motive for Saturday's attack was not known, government ministers had warned that there could be other “Islamist militant” attacks. President Emmanuel Macron has deployed thousands of soldiers to protect sites such as places of worship and schools.
Prime Minister Jean Castex, who was visiting Rouen, said he was heading back to Paris to assess the situation.
The Nice attack took place on the day Muslims celebrate the Prophet Mohammad's birthday. Many Muslims around the world have been angered about France's defense of the right to publish cartoons depicting the Prophet.
A third person has been taken into police custody in connection with that attack, a police source said on Saturday. The suspected assailant was shot by police and remained in critical condition in hospital.