Both men were alone in the mosque in La Grand-Combe, a former mining town in the Gard region, last Friday when the victim was fatally stabbed. The assailant reportedly recorded the attack on his phone and filmed the dying Malian man, who was in his 20s.

A source close to the case, who asked not to be named, said the suspected perpetrator, while not apprehended, has been identified as a non-Muslim, French citizen of Bosnian origin, according to the AFP news agency.

After initially praying alongside the man, the attacker stabbed the victim about 50 times before fleeing the scene. The body was found later in the morning, when other worshippers arrived at the mosque for Friday prayers.

The suspect, who has been identified only as Olivier – born in France in 2004 and unemployed, with no criminal record – is “potentially extremely dangerous” and it is “essential” to arrest him before he claims more victims, according to regional prosecutor Abdelkrim Grini.

The Grand Mosque of Paris condemned the attack in a statement and said the victim had just finished cleaning the mosque when he was killed.

It called on authorities to quickly shed light on the reasons behind the attack, asking judicial authorities to say whether it is being treated as a “terrorist” act and to note its “scale and seriousness … for the safety of all”.

“Racism and hatred based on religion can have no place in France. Freedom of worship cannot be violated,” President Emmanuel Macron wrote on X on Sunday in his first comments on the killing, extending his support to “our fellow Muslim citizens”.

Justice Minister Gerald Darmanin on Saturday decried the “despicable murder” that “wounds the hearts of all believers, of all Muslims in France”.

“We stand shoulder to shoulder with the victim’s family and the shocked worshippers,” he said. “The resources of the state are being mobilised to ensure that the murderer is caught and punished.”

Interior Minister Bruno Retailleau announced on Sunday that he would travel to La Grand-Combe. (Al Jazeera/AFP)