Thousands of people rallied in central Paris Sunday in a defiant show of solidarity with a teacher beheaded for showing pupils cartoons of the Prophet Mohammed.
Demonstrators on the Place de la Republique held aloft posters declaring: "No to totalitarianism of thought" and "I am a teacher" in memory of the decapitated victim Samuel Paty.
Some chanted "I am Samuel", echoing the "I am Charlie" cry that travelled around the world after Islamist gunmen killed 12 people at the Charlie Hebdo satirical magazine in 2015 for publishing caricatures of the Islamic prophet.
Between bursts of applause, others recited: "Freedom of expression, freedom to teach."
Demonstrations are also planned for the cities of Lyon, Toulouse, Strasbourg, Nantes, Marseille, Lille and Bordeaux.
Paty's assassination has shocked the country and brought back memories of a wave of Islamist violence in 2015 that started with the Charlie Hebdo massacre.
Those killings saw some 1.5 million people gather on the Place de la Republique in support of freedom of expression.
Ahead of Sunday's gathering, Education Minister Jean-Michel Blanquer called on "everyone to support the teachers", telling broadcaster France 2 that it was vital to show "our solidarity and unity".
Prime Minister Jean Castex and Paris mayor Anne Hidalgo were among those present.
"I am here as a teacher, as a mother, as a Frenchwoman and as a republican," said Virginie, one of those gathered.
On Saturday, anti-terror prosecutor Jean-Francois Ricard said Paty had been the target of online threats prior to his murder for showing the cartoons to his civics class.
Depictions of the prophet are widely regarded as taboo in Islam.
A photo of the teacher and a message confessing to his murder was found on the mobile phone of his killer, 18-year-old Chechen Abdullakh Anzorov, who was shot dead by police.
Witnesses said the suspect was spotted at the school on Friday asking pupils where he could find Paty.
The father of one schoolgirl had launched an online call for "mobilisation" against the teacher and had sought his dismissal from the school.
The girl's father and a known Islamist militant are among those arrested, along with four members of Anzorov's family.
An 11th person was taken into custody on Sunday, a judicial source said, without providing details.
The aggrieved father had named Paty and gave the school's address in a social media post just days before the beheading which President Emmanuel Macron has labelled an Islamist terror attack.
Ricard did not say if the attacker had any links to the school, pupils or parents, or had acted independently in response to the online campaign.
The prosecutor said the attacker had been armed with a knife, an airgun and five canisters. He had fired at police and tried to stab them as they closed in on him.
He was in turn shot nine times.
The Russian embassy in Paris said the suspect's family had arrived in France from Chechnya when he was six and requested asylum.
Locals in the Normandy town of Evreux where the attacker lived described him as low key, saying he got into fights as a child but calmed down as he became increasingly religious in recent years.
Friday's attack was the second of its kind since a trial started last month over the January 2015 Charlie Hebdo massacre.
The magazine republished the cartoons in the run-up to the trial, and last month a young Pakistani man wounded two people with a meat cleaver outside the magazine's former office.
Ricard said Paty's murder illustrated "the very high-level terrorist threat" France still faces but added the attacker was not known to French intelligence services.
'Doing his job'
On Saturday, hundreds of pupils, teachers, parents and sympathisers flooded to Paty's school to lay white roses.
"For the first time, a teacher was attacked for what he teaches," said a teacher from a neighbouring town who gave only his first name, Lionel.
According to parents and teachers, Paty had given Muslim children the option to leave the classroom before he showed the cartoons, saying he did not want their feelings hurt.
And Kamel Kabtane, rector of the mosque of Lyon and a senior Muslim figure, said Sunday that Paty had merely been "doing his job" and was "respectful" in doing so.
"These terrorists are not religious but are using religion to take power," Kabtane told AFP.
Ministers who form France's defence council were to meet Sunday to discuss the Islamist threat.
A national tribute is to be held for Paty on Wednesday.