French President Emmanuel Macron sought to calm flaring tensions with Muslims around the world on Saturday, telling an Arab TV channel he understood that caricatures of Prophet Muhammad (peace be upon him) 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 caricatures of the Holy Prophet (peace be upon him) by the Charlie Hebdo weekly, which was followed by an attack outside its former offices, the beheading of a teacher and an attack on a church in Nice Thursday that left three dead.

The country was further shaken by a new incident on Saturday, when an attacker armed with a sawn-off shotgun shot an Orthodox priest as he closed his church in the French city of Lyon before fleeing, a police source said.

The 52-year-old priest, who has Greek nationality, was shot in the liver point-blank range and taken to hospital in serious condition, sources said.

Police were searching for the assailant and warned residents to avoid the area. The attacker's motive remains unclear.

- Softer tone -

Macron sparked protests across the Muslim world after the murder earlier this month of teacher Samuel Paty -- who had shown his class caricatures of the Holy Prophet (peace be upon him) -- 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."

- 'Relied on lies' -

Macron lashed out at "distortions" from political leaders over the issues, saying too often people were led to believe that they were a creation of the French state.

He slammed "a confusion that has been fed by many media -- and sometimes political and religious leaders -- which is to say that these caricatures are in a way the project or the creation of the French government or the president".

He also denounced calls for a boycott of French goods, backed in particular by Turkish President Recep Tayyip Erdogan and taken up by some retailers in Muslim countries, as "unworthy" and "unacceptable".

He said the campaign was created by some private groups "who relied on lies... sometimes from other leaders" about the caricatures.

Even before the attack on Paty, Macron had promised a tough new campaign against radicalism in France, which has claimed the lives of hundreds of people since 2015.

Protests erupted Friday in Afghanistan, Pakistan, Bangladesh, Mali, Mauritania and Lebanon, the latest in a string of mass rallies denouncing France.

- '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 on Saturday arrested another Tunisian man, bringing to four the number of people being held in connection with the deadly attack in Nice.