France will see people descend onto the streets to show their support for freedom of speech and commemorate the life of the history teacher who was beheaded near Paris after showing his pupils caricatures of the Prophet Muhammad.
Samuel Paty, who taught history and geography, was decapitated on Friday by an 18-year-old Moscow-born Chechen refugee, who was then shot dead by police.
Political leaders, associations and unions will rally on Sunday afternoon in Paris and other major French cities such as Lyon, Toulouse, Strasbourg, Nantes, Marseille, Lille and Bordeaux.
The gatherings come as French authorities said they have detained a 10th person in the wake of the gruesome attack in Conflans-Sainte-Honorine, which is 30 km (20 miles) northwest of Paris.
French anti-terrorism prosecutor Jean-Francois Ricard said an investigation for murder with a suspected terrorist motive has been opened.
At least four of those detained are family members of the attacker, who had been granted a 10-year residency in France as a refugee in March. He 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, Mr Ricard said. He did not 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”.
The attack has sparked global condemnation – with President Emmanuel Macron saying the nation’s fight against Islamic terrorism is “existential”.
The teacher had received threats after opening a discussion “for a debate” about caricatures about 10 days ago, a police official told the Associated Press. The parent of a student had filed a complaint against the teacher, another police official said.
On Saturday, Prime Minister Jean Castex said France will react with the greatest firmness after the teacher was decapitated.
“Through one of its defenders, it is the Republic which has been struck in the heart by Islamist terrorism,” Mr Castex tweeted.
“In solidarity with its teachers, the State will react with the greatest firmness so that the Republic and its citizens live, free! We will never give up. Never.”
Additional reporting by agencies