A priest was killed on Tuesday when two armed assailants seized hostages at a church near the northern French city of Rouen, police said.
Five people were inside the church in the Normandy town of Saint-Etienne-du-Rouvray when it came under attack, interior ministry spokesman Pierre Henry Brandet said.
He said the church was surrounded by France’s anti-gang brigade the BRI, which specialises in kidnappings, and that “the two assailants came out and were killed by police”.
Three of the hostages were freed unharmed, and another was fighting for their life. A police source said the priest of the Saint-Etienne church was killed.
The motivations for the hostage-taking were not yet clear, but the Paris prosecutor’s office said the case was being handled by anti-terrorism prosecutors.
The incident comes as France remains on high alert nearly two weeks after Tunisian Mohamed Lahouaiej Bouhlel ploughed a truck into a crowd of people celebrating Bastille Day in the French Riviera city of Nice, killing 84 people and injuring over 300.
French President Francois Hollande, who is from Rouen, and Interior Minister Bernard Cazeneuve were on their way to the scene, their offices said.
An AFP journalist said the scene of the attack was crawling with emergency vehicles and police.
French prime minister Manuel Valls expressed his horror at what he called “a barbaric attack on a church”.
“The whole of France and all Catholics are wounded. We will stand together,” he wrote on Twitter.
Pope Francis voiced his “pain and horror” at the hostage-taking, according to the Vatican.
The archbishop of Rouen, Dominique Lebrun, urged all non-believers to join those of the church in “calling to God”.
“The Catholic Church can take up no other weapons that prayer and fraternity between men,” he said in a statement.
The Nice attack was the third major strike on France in 18 months and was claimed by the Islamic State group.
Two attacks in Germany claimed by the Islamic State group since then have also increased jitters in Europe.
After the attack in Nice, France extended a state of emergency giving police extra powers to carry out searches and place people under house arrest for another six months until January.
It was the fourth time the security measures have been extended since Islamic State jihadists struck Paris in November, killing 130 people at restaurants, a concert hall and the national stadium.
Bitter political feud
The Nice massacre has triggered by a bitter political spat over alleged security failings, with the government accused of not doing enough to protect the population.
French far-right National Front leader Marine Le Pen wrote on Twitter that the “modus operandi obviously makes us fear a new attack from terrorist Islamists.”
Valls had warned earlier in the week that the country will face more attacks as its struggles to handle extremists returning from jihad in the Middle East and those radicalised at home by devouring propaganda on the internet.
France has been concerned about the threat against churches ever since a foiled plot against in the Paris suburb of Villejuif in April last year.
Sid Ahmed Ghlam, a 24-year-old Algerian IT student, was arrested in Paris on suspicion of killing a woman who was found shot dead in the passenger seat of her car, and of planning an attack on a church.
Prosecutors say they found documents about al Qaeda and IS at his home, and that he had been in touch with a suspected jihadist in Syria about an attack on a church.