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 been carrying a weapon when he was arrested.
The priest, who has Greek nationality, was closing his church when the attack happened and is now in a serious condition, said the source, who asked not to be named.
The shooting comes three days after three people were killed in a knife rampage inside a church in the southern town of Nice.
A Tunisian suspect was shot by police near the scene of that attack.
France was already on edge after the republication in early September of cartoons of the prophet Mohammed by the Charlie Hebdo weekly, which was followed by an attack outside its former offices, the beheading of a teacher, and the attack in Nice.
Foreign Minister Jean-Yves Le Drian has warned that French citizens face a security risk "wherever they are", saying alerts had been sent to all French nationals abroad.
France went into a second coronavirus lockdown on Friday but the government has exempted places of worship until Monday, allowing them to celebrate the Christian All Saints' Day on Sunday.
France has been on high alert since the January 2015 massacre at the satirical weekly magazine Charlie Hebdo marked the beginning of a wave of jihadist attacks that have killed more than 250 people.
Tensions have heightened since last month, when the trial opened for 14 suspected accomplices in that attack.
After the deadly attack in Nice, President Emmanuel Macron announced increased surveillance of churches by France's on-the-street military force, which is to be bolstered to 7,000 troops from 3,000.
Security at schools will also be boosted, he said. Schools are remaining open during the new lockdown.
Calming tensions
President Emmanuel Macron on Saturday sought to calm flaring tensons with Muslims around the world, telling an Arab TV channel he understood that caricatures of the Prophet Mohammed could be shocking while lashing out at "lies" that the French state was behind them.
France is on edge after the republication in early September of cartoons of the prophet by the Charlie Hebdo weekly, which was followed by an attack outside its former offices, the beheading of a teacher and an attack Thursday on a church in Nice that left three dead.
Macron sparked protests in the Muslim world after the murder earlier this month of teacher Samuel Paty — who had shown his class a cartoon of Mohammed — by saying France would never renounce its laws permitting blasphemous caricatures.
But in an apparent bid to reach out to Muslims, Macron gave a long interview setting out his vision to Qatar-based TV channel Al-Jazeera, seeking to strike a softer tone.
"I can understand that people could be shocked by the caricatures, but I will never accept that violence can be justified," he said.
"I understand the feelings that this arouses, I respect them. But I want you to understand the role that I have. My role is to calm things down, as I am doing here, but at the same time it is to protect these rights."
He added: "I will always defend in my country the freedom to speak, to write, to think, to draw."
'Too early to say'
France is still reeling from the latest attack in Nice which Macron has already described as "Islamist" terror.
French authorities were on Saturday seeking to ascertain if a young Tunisian suspected of killing three people in a knife rampage inside a Nice church had outside help.
Brahim Issaoui, 21, only arrived in Europe from Tunisia last month and, according to prosecutors, killed a church employee, a Brazilian woman and a French woman in the attack in the Notre-Dame Basilica on Thursday morning.
The attacker cut the throat of Nadine Devillers, 60, and the sexton Vincent Loques, 55. A Brazilian mother, Simone Barreto Silva, who was stabbed several times, took refuge in a nearby restaurant but died of her wounds there.
Issaoui was shot by police multiple times and is currently in a grave condition in hospital. Investigators have been unable to question him and his precise motivations remain unclear.
"It is still too early to say if there were others complicit, what his motivations were in coming to France and when this idea took root in him," said a source close to the inquiry who asked not to be named.
Investigators believe Issaoui travelled illegally to Europe via Italy's Mediterranean island of Lampedusa on September 20.
He arrived at the mainland Italian port of Bari on October 9 before coming to Nice just one or two days before the attack.
French police are currently holding three people for questioning in the investigation, which is focusing on two telephones found on the suspect after the attack.