A nun has described how 84-year-old priest, Jacques Hamel, was forced to kneel on the floor before his throat was slit at a church in Normandy in France.
The two attackers killed the clergyman celebrating Mass and gravely injured one of the few worshipers present before being shot dead by police.
The Sister, who escaped, said she saw the attackers video themselves and “give a sermon in Arabic” around the altar at the church near Rouen.
The Islamic State group claimed responsibility for the first attack on a church in the West.
Police rescued three other people in the building – including a second nun – in the small north-western town of Saint-Etienne-du-Rouvray, said Interior Ministry spokesman Pierre-Henry Brandet.
A regional Muslim leader said one of the two attackers – both killed outside the church – was known to police. A police official said he had tried to go to Syria.
It was the first known attack claimed by IS inside a church in the West. A church outside Paris was targeted last year, but the attack was never carried out.
A statement by the Islamic State-affiliated Amaq news agency said the attack was carried out by “two soldiers of the Islamic State” in response to calls to target nations in the US-led coalition fighting IS in Iraq and Syria.
The statement echoed claims in other recent attacks in France and neighboring Germany. It repeated its threat to Western “crusaders”. The RAID special intervention force searched for possible explosives in or around the church.
The nun said the priest was forced to the ground before his throat was slit.
Identified as Sister Danielle, she told BFM television: “They forced him to his knees. He wanted to defend himself, and that’s when the tragedy happened.”
She said the attackers recorded themselves. “They did a sort of sermon around the altar in Arabic. It’s a horror.”
Dominique Lebrun, the Archbishop of Rouen, confirmed the death of 84-year-old Rev Jacques Hamel. “I cry out to God, with all men of goodwill. And I invite all non-believers to unite with this cry,” Rev Lebrun wrote in a statement from Krakow, Poland.
“The Catholic Church has no other arms besides prayer and fraternity between men.”
French President Francois Hollande, arriving at the scene, called it a “vile terrorist attack” and one more sign that France was at war with the Islamic State group, which has claimed a string of attacks on the country and two in Germany.
Town mayor Hubert Wulfranc, in tears, denounced the “barbarism” and, breaking down, pleaded: “Let us together be the last to cry.”
A police official said one of the attackers had been turned back after trying to go to Syria. The official said the man was under police supervision and 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 one-and-a-half years. He went to Turkey and security services were alerted after this,” he said.
The Pope condemned the attack in the strongest terms.
Vatican spokesman the Rev Federico Lombardi said Pope Francis expressed his “pain and horror for this absurd violence, with the strongest condemnation for every form of hatred and prayer for those affected”.
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 and was claimed by Islamic State, as well as a series of attacks last year which 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.