Muslims have attended Catholic Sunday mass in churches around France to express solidarity and sorrow following the brutal jihadist murder of a priest in Normandy, the latest in a series of attacks.

More than 100 Muslims were among the 2,000 faithful who packed the 11th-century Gothic cathedral of Rouen where two jihadi teenagers slit the throat of 85-year-old Father Jacques Hamel, Agence France-Presse reported.

"I thank you in the name of all Christians," Rouen Archbishop Dominique Lebrun told them July 31. "In this way you are affirming that you reject death and violence in the name of God."

In Nice, Otaman Aissaoui, Nice's top imam, led a delegation to a Catholic mass in the Mediterranean city where a jihadist had carried out a rampage in a truck on July 14, claiming 84 lives and injuring 435 including many Muslims.

"Being united is a response to the act of horror and barbarism," he said.

The Notre Dame church in southwestern Bordeaux also welcomed a Muslim delegation, led by the city's top imam Tareq Oubrou.

On the papal plane returning from World Youth Day in Krakow, Poland, Pope Francis denied that Islam itself is violent and insisted that the potential for violence lies within every religion, including Catholicism.

Pope Francis answered reporters questions on board a flight from Krakow, Poland, to Rome, at the end of his 5-day trip to southern Poland, July 31.

AVOIDANCE OF TERM 'ISLAMIC VIOLENCE'

Francis defended his avoidance of the term "Islamic violence" by suggesting the potential for violence lies in every religion, including Catholicism, Crux News reports.

"I don't like to talk about Islamic violence, because every day, when I read the newspaper, I see violence," Francis said.

He gave this answer when asked about why he never speaks of Islamic terrorism or fundamentalism when condemning attacks such as the murder of the French priest in Normandy, who had his throat slit by an Islamic terrorist as he was celebrating Mass.

The Pope said that when he reads the newspaper, he reads about an Italian who kills his fiancé or his mother in law.

"They are baptized Catholics. They are violent Catholics," Francis said, adding that if he speaks of "Islamic violence," then he has to speak of "Catholic violence" too.

The pontiff made his remarks after the five-day visit to Poland in which Francis presided over World Youth Day, a gathering of Catholic youth from all around the world in Krakow, Poland.

He said that in every religion there are violent people, "a small group of fundamentalists," including in Catholicism.

"When fundamentalism goes as far as murdering ... you can murder with your tongue and also with the knife," he said.

"I believe that it's not fair to identify Islam with violence. It's not fair and it's not true," note Francis, saying that he's had a long conversation with the Grand Imam of Al-Azhar, the Cairo-based Islamic university often described as the Vatican of the Sunni world.

"I know how they think. They look for peace, encounter," he said.