Two attackers took hostages inside a French church during morning Mass on Tuesday near the city of Rouen, killing an 86-year-old priest by slitting his throat before being shot and killed by police, French officials said. The Islamic State group claimed responsibility for the attack.

Another person inside the church in Normandy was seriously injured and is hovering between life and death, Interior Ministry spokesman Pierre-Henry Brandet said. Police managed to rescue the only three other people inside the church in the small northwestern town of Saint-Etienne-du-Rouvray, he told reporters.

A regional Muslim leader said one of the two attackers — who were killed outside the church — was known to police.

It was the first known attack inside a French church in recent times. A church was targeted last year, but the attack never was carried out.

A statement published by the Islamic State-affiliated Amaq news agency said the attack was carried out by “two soldiers of the Islamic State” who acted in response to calls to target nations in the U.S.-led coalition fighting IS in Iraq and Syria.

The RAID special intervention force was searching for possible explosives in or around the church.

“The investigations are ongoing. There are still unknowns,” Brandet said. “There are dogs, explosive detectors and bomb disposal services and as long as there are still unknowns, the judicial police cannot get inside the site. It’s a dramatic situation.”

Dominique Lebrun, the archbishop of Rouen, confirmed the death of 86-year-old Rev. Jacques Hamel.

“I cry out to God, with all men of good will. And I invite all non-believers to unite with this cry,” Lebrun wrote in a statement from Krakow, Poland, where Pope Francis was expected. “The Catholic Church has no other arms besides prayer and fraternity between men.”

French President Francois Hollande, arriving on the scene, called it a “vile terrorist attack” and said it’s one more sign that France is at war with the Islamic State, which has claimed a string of attacks on France.

“We must lead this war with all our means,” he said, adding that he was calling a meeting on Wednesday of representatives of all religions.

He expressed solidarity with local Catholics, saying “they have been terribly hit by the killing of the parish priest by two terrorists claiming to belong to Daesh. I have met with the family of the priest.”

A police official said one of the attackers was turned back after trying to go to Syria. The official, who spoke on condition of anonymity to reveal details of the investigation, said the man wore an electronic bracelet to monitor his movements.

Mohammed Karabila, head of the Regional Council of the Muslim Faith for Haute-Normandie, said French security services knew the name of one of the attackers.

“The person who committed this odious act is known and he has been followed by the police for at least 1 1/2 years. He went to Turkey and security services were alerted after this,” he told The Associated Press by phone. He refused to divulge man’s name and had no information on the second attacker.

The pope condemned the attack in the strongest terms. Vatican spokesman, the Rev. Federico Lombardi, said in a statement the attack hits particularly hard “because this horrific violence took place in a church, a sacred place in which the love of God is announced, and the barbaric murder of a priest.”

France is on high alert and under a state of emergency after an attack in the southern city of Nice on Bastille Day — July 14 — that killed 84 people that was claimed by the Islamic State group, as well as a series of attacks last year that killed 147 others around Paris.

Islamic State extremists have urged followers to attack French churches and the group is believed to have planned at least one church attack earlier.

The attack once again demonstrates the challenge of combating the threat. French authorities increased security at churches, synagogues, mosques and other places of worship after attacks in Paris last year, but ensuring constant, blanket security is difficult in a country with a church in every town and village.

In April 2015, an Algerian student who was arrested after shooting himself in the leg was found with heavy weapons, bulletproof vests and documents linked to Islamic State. He is charged with killing a young woman inside her car the same day. According to French authorities, the suspect, Sid Ahmed Ghlam, was sent by the Belgian Abdelhamid Abaaoud to attack a church in Villejuif, just outside of Paris.

A cell directed by Abaaoud later carried out the Nov. 13 attacks in Paris that left 130 people dead and the March 22 attacks in Brussels that killed 32 people.

(AP)