French President Francois Hollande said two "terrorists claiming to be followers of Islamic State" have entered a church in northern France, killing an 84-year-old priest and seriously wounding another person.
French officials said the two assailants were killed by police, who had surrounded the area when they left the church.
Interior Ministry spokesman Pierre-Henry Brandet said that a search for explosives around the perimeter began shortly thereafter.
The hostage-taking began at the time that Mass was being said in the church, located in Saint-Etienne-du-Rouvray in the north-eastern region of Upper Normandy, French media reported. The archbishop of nearby Rouen identified the priest as Jacques Hamel.
Soon after Hollande's statement, the Islamic State extremist group claimed that the killers were two of its "soldiers".
They made the claim in a statement released via its Aamaq Agency's channels on the Telegram messaging app, similar to recent claims of responsibility by the group.
The attack came in response to Islamic State's calls for attacks on states taking part in the international coalition fighting it, Aamaq said.
In France, the attack prompted condemnation and calls not to allow the latest in a string of Islamist-motivated attacks to divide the French people.
"We are confronted by Islamic State, which has declared war on us," Hollande said.
"We must conduct this war by all means, respecting the rights that make us a democracy. What the terrorists want is to divide us."
He said that he would receive the archbishop of Normandy on Tuesday evening, followed by a meeting with leaders from all the religions in France.
"It is all French who have been touched. This is why we must remain together, within a unified group, in a bloc that no one is able to break apart."
Pope Francis shared the pain caused by the murder, the Vatican said in a statement.
"The Pope is informed and shares the pain and horror for this absurd violence, most radically condemns all forms of hatred and prays for people hurt," Vatican spokesman Father Federico Lombardi said in a statement.
"We are particularly struck because this horrible violence has taken place in a church, a sacred place where the love of God is announced, with the brutal killing of a priest," Lombardi added.
