Demonstrations were held across France on Sunday in tribute to a teacher who was beheaded by an attacker after showing his students caricatures of Mohammad.
Samuel Paty was murdered near the school where he worked, in the commune of Conflans Saint-Honorine, northwest of Paris, on Friday.
The suspected killer, who officials said was an 18-year-old Chechen refugee, was armed with a knife and a plastic pellet gun, was later shot dead by officers in a nearby town, police said.
French authorities have launched an anti-terror investigation.
President Emmanuel Macron called it an "assassination" and an "Islamist terrorist attack".
The leaders of the main political parties, associations and trade unions joined demonstrations on Sunday afternoon in Paris, Place de la République, and in many other cities including Lyon, Toulouse, Strasbourg, Nantes, Marseille, Lille and Bordeaux.
The Minister of Education Jean-Michel Blanquer and the Minister Delegate for Citizenship Marlène Schiappa said they would represent the government "in support of teachers, secularism, freedom of expression and against Islamism".
Here's what we know about the attack so far:
Who was the victim?
Paty, a 47-year-old history and geography teacher, was decapitated near the school at around 5 pm local time.
Police told the AFP news agency that he had hosted a class discussion with secondary school students about cartoons of Islam's Prophet Mohammad.
Some Muslim parents said they had complained to the school and French media reported Paty had received a number of threats in the wake of the class.
Although it is not mentioned in the Quran, making an image of the Prophet is considered idolatry by some Muslims, particularly in the more hardline Sunni tradition.
Blanquer said the school had taken "appropriate" steps in response to the complaints in setting up measures that both "supported the teacher and opened up a dialogue with parents".
The minister added he would prepare a pedagogical "framework" on how to address the attack with students when they returned to school after half term. He said a minute's silence would be organised.
Macron visited the Bois d'Aulne school and met the history teacher's colleagues on Friday evening.
He said afterwards: "One of our citizens was assassinated tonight because he was a teacher, because he taught students about the liberty of expression, the liberty to believe or not to believe.
"Our countryman was the victim of a cowardly attack. The victim of an Islamist terrorist attack."
Who was the alleged perpetrator?
His alleged attacker was reported to be 18 years old, of Chechen origin and born in Moscow.
Officials said he was shot dead in the neighbouring town of Éragny after he acted in a threatening manner and failed to respond to an order to put down his weapons.
Officials said he was unknown to intelligence services.
French anti-terrorism prosecutor Jean-Francois Ricard told reporters the suspect, who had been granted a 10-year residency in France as a refugee in March, was armed with a knife and an airsoft gun, which fires plastic pellets.
His half-sister joined the Islamic State group in Syria in 2014, Ricard said. He didn't give her name, and it is not clear where she is now.
The prosecutor said a text claiming responsibility and a photograph of the victim were found on the suspect's phone.
He also confirmed that a Twitter account under the name Abdoulakh A belonged to the suspect. It posted a photo of the decapitated head minutes after the attack along with the message “I have executed one of the dogs from hell who dared to put Muhammad down.”
Ricard said the suspect had been seen at the school asking students about the teacher, and the headmaster had received several threatening phone calls.
France’s anti-terrorism prosecutor’s office said authorities investigating the killing arrested nine suspects, including the teen's grandfather, parents and 17-year-old brother.
What's the background to this attack?
The incident came as the French government works on a bill to address Islamist radicals who authorities claim are creating a "parallel society outside the values of the French Republic".
This marks the second terrorism-related incident since a trial began into the January 2015 massacre at the satirical magazine Charlie Hebdo, which had published cartoons depicting Mohammad.
The magazine republished them this year as the trial got underway.
Three weeks ago, an 18-year-old from Pakistan was arrested after stabbing two people outside the former Charlie Hebdo offices.
He told police he was upset about the publication of the caricatures. His victims suffered non-life-threatening injuries.
How have people reacted to the incident?
Chaired by Macron, the country's Defence Council decided on Sunday to strengthen security at schools at the start of the school year, as well as to take "concrete action" against groups or individuals who sent messaged of hatred after the murder.
Macron "called for swift action to be taken and for no respite to be given to those who organise to oppose the republican order," the Elysée added.
Politicians across the political spectrum have denounced the murder, and took part in demonstrations against extremism on Sunday.
Charlie Hebdo tweeted on Friday: "Intolerance just reached a new threshold and seems to stop at nothing to impose terror in our country."
European Commission President Ursula von der Leyen on Saturday expressed her condolences to the victim's family and said her "thoughts were going out to teachers in France and throughout Europe" after the attack.
"Without them (teachers), there are no citizens. Without them, there is no democracy," she added.
The Assembly of Chechens in Europe, which is based in Strasbourg, France, said in a statement: "Like all French people our community is horrified by this incident."
The rector of the Lyon mosque, Kamel Kabtane, said that the murdered teacher "did his job" and was "respectful" in teaching his pupils about freedom of expression.
He condemned the perpetrator, saying he had proved by his actions that he was "not religious".
Paty "was entitled to raise the intellectual level on tolerance and freedom of expression," he said.
"He was respectful and he even suggested to students who might feel shocked to go out. He wanted to speak without offending, without hurting," Kabtane said in an interview with AFP.