The attack on a church near Rouen in northern France comes just 12 days after a lorry attack on people celebrating Bastille Day in Nice.
They are the latest in a series of deadly attacks in France that have been getting more frequent in recent years.
Previous attacks have included the killing of soldiers and schoolchildren by a lone gunman in the Toulouse region, shootings at the Charlie Hebdo offices in Paris, and a co-ordinated assault by gunmen and suicide bombers on a concert hall, a major stadium, restaurants and bars in Paris.
11-22 March, Toulouse and Montauban: Gunman Mohammed Merah, 23, a French citizen of Algerian extraction, killed three soldiers on 11 and 15 March, before shooting three children and a teacher at a Jewish school on 19 March.
He was eventually killed on 22 March during a lengthy police siege at his flat in Toulouse.
23 May, La Defense, Paris: A French soldier was stabbed in the neck by a convert to Islam, named as Alexandre Dhaussy. The soldier survived.
20 December, Joue-les-Tours: A Burundi-born French national attacked three police officers with a knife, shouting "God is great!" in Arabic. He was shot dead by police.
21 December, Dijon: A driver shouting "God is great" in Arabic ran down pedestrians in Dijon, eastern France, injuring 11 people.
22 December, Nantes: At a Christmas market in western France, 10 people were injured when a van drove into pedestrians, before the driver attempted suicide.
7-9 January, Charlie Hebdo offices and Hypercacher supermarket, Paris: Brothers Said and Cherif Kouachi attacked the offices of French magazine Charlie Hebdo in Paris, killing 12 people including the editor and celebrated cartoonists. The following day a policewoman was murdered by Amedy Coulibaly, who then held up a Jewish supermarket, killing four people. The Kouachi brothers and Coulibaly were all killed after separate hostage stand-offs with police.
3 February, Nice: A man wielding a knife attacked and wounded three soldiers patrolling outside a Jewish community centre in Nice. The attacker was named as Moussa Coulibaly, a Malian with no apparent link to the Paris gunman of the same surname.
19 April, Villejuif, Paris: Sid Ahmed Ghlam, a 24-year-old Algerian national, was arrested by police after he apparently shot himself by accident. Investigators believe he was planning attacks on "one or two churches" in the Paris suburbs. He was charged with terror offences and the murder of a woman found in a burning car.
26 June, Saint-Quentin-Fallavier: A man was found decapitated and several others injured at a factory near Lyon. Several explosions were heard and one of the suspects was arrested by police. French President Francois Hollande has described it as a terrorist attack.
21 August, Oignies: A mass shooting was averted on a high-speed train travelling between Amsterdam and Paris, when a passenger armed with an automatic pistol and a box cutter was subdued by six passengers. Three people were injured in the struggle, which took place on a section of track in northern France.
13-14 November, Paris: Gunmen and suicide bombers hit a concert hall, a major stadium, restaurants and bars, almost simultaneously - and left 130 people dead and hundreds wounded. The deadliest attack of the night came at a concert venue on Boulevard Voltaire, where Californian rock group Eagles of Death Metal was playing. Eighty-nine people died as the men fired Kalashnikov-type assault rifles into the crowd.
1 January, Valence: A man was shot in south-eastern France after he reportedly drove a car at four soldiers who were guarding a mosque. One of the soldiers was injured, and a stray bullet hit an elderly bystander in the calf.
7 January, Paris: A man who was apparently trying to attack a police station on the anniversary of the Charlie Hebdo attacks was shot dead by police. The suspect was carrying a meat cleaver and wearing a dummy suicide vest.
13 June, Magnanville: A French police commander and his partner were stabbed to death at their home west of Paris by a man claiming allegiance to so-called Islamic State (IS). Their three-year-old survived. The attacker was killed in an police assault on the house.
14 July, Nice: At least 84 people were killed, including children, after a lorry slammed through a crowd celebrating Bastille Day in the southern French city of Nice. The driver ploughed on for 2km (1.2 miles) on the Promenade des Anglais at about 23:00 local time, before being shot dead by police. Witnesses say the speeding lorry swerved and zigzagged in an apparent attempt to hit more people.
26 July, Saint-Etienne-du-Rouvray: A priest was killed in an attack by two armed men on a church in a suburb of Rouen in northern France. The attackers entered the church in Saint-Etienne-du-Rouvray during Mass, taking the priest, Fr Jacques Hamel, 84, and four other people hostage, before being shot dead by police. President Hollande said the men claimed to be from IS.