Two teenagers who murdered an elderly French priest a year ago after pledging loyalty to the Islamic State group failed to sow religious division, President Emmanuel Macron told a memorial service Wednesday.

Jacques Hamel, 85, was conducting mass in the northern town of Saint-Etienne-du-Rouvray, near Rouen, when the attackers burst in and slit his throat in front of five worshippers.

The gruesome attack caused widespread horror, coming two weeks after a radical used a truck to crush 86 people to death in the southern city of Nice.

In a video, the teenagers had sworn allegiance to IS.

At Wednesday's memorial in Hamel's small 16th-century church Macron hailed the solidarity shown by French Muslims after the attack -- and the failure of Catholics to be provoked.

"The two terrorists thought they would sow a desire among French Catholics for revenge. They failed," he said.

While assuring that the French state was "not out to combat any religion", Macron added that every religion "has its part to play to ensure that hatred... never wins.

"It is a long battle, waged every day," he added. "Here, you won it."

Three nuns and an elderly couple witnessed Hamel's murder by Adel Kermiche and Abdel Malik Petitjean on a quiet midweek morning in July.

The 19-year-old killers, who had been on a terror watch list, were shot dead by police outside the church.

Hundreds of people, including relatives of Hamel, two government ministers and representatives of the French Council for the Muslim Faith were packed in at Wednesday's mass.

Outside, where Macron unveiled a large stainless steel disk inscribed with the Universal Declaration of Human Rights, an overflow crowd followed the proceedings on a giant screen.

Rouen Archbishop Dominique Lebrun, who led the ceremony, thanked the Muslim community for asking to be included in the commemorations.

Later Wednesday, after evening prayers, dozens of people went to pay their respects to the priest at his grave in a nearby cemetery, including representatives from the local Muslim community. 

Two people have been charged over their suspected links to the attackers.

One is a cousin of Petitjean's, whom investigators suspect knew of the plot to kill the priest.

Hamel, meanwhile, is on track to be beatified by the Vatican as a martyr -- a first step towards sainthood.

Source: APF