People gather in front of the Bois d’Aulne college after the attack in the Paris suburb of Conflans St Honorine, France, October 17, 2020. Photo: REUTERS/Charles Platiau.

An eleventh person was detained on Sunday, police said, as authorities investigated the murder of Samuel Paty, a history teacher who was beheaded by a suspected Islamist in an attack that stunned the country.

Satirical magazine Charlie Hebdo, whose offices were attacked in a mass killing five years ago, was among groups organizing a tribute to Paty in Paris in the afternoon.

The 47-year-old teacher was killed on Friday outside his school in a Paris suburb by an 18-year-old attacker. The assailant, who was born in Russia of Chechen origin, was shot dead by police soon after the attack.

Earlier this month, the teacher had shown his pupils cartoons of the Prophet Mohammad in a class on freedom of expression, angering a number of Muslim parents. Muslims believe that any depiction of the Prophet is blasphemous.

The government has portrayed the killing as an attack on the heart of French values.

Education Minister Jean-Michel Blanquer and politicians from across the spectrum were due to attend Sunday’s commemoration in central Paris. A national tribute will be organized for Wednesday, President Emmanuel Macron’s office said.

Prime Minister Jean Castex said the government was working on a strategy to better protect teachers from threats. Paty had been the target of an angry campaign on social media before the attack.

“I want teachers to know that, after this ignoble act, the whole country is behind them,” Castex told the Journal du Dimanche in an interview.

“This tragedy affects each and every one of us because, through this teacher, it is the Republic that was attacked.”

There were no details of the eleventh person to be detained in connection with the killing.

Four close relatives of the attacker were detained soon after the attack. Five more were later detained, including the father of a pupil at Paty’s school and an acquaintance of the pupil’s father known to the intelligence services, anti-terrorism prosecutor Jean-Francois Ricard said on Saturday.

A tenth person was placed in custody later on Saturday.

Macron was due to hold a security meeting with key ministers later on Sunday, his office said.

On Saturday, hundreds of people, including pupils and their parents, teachers and local residents came to express their grief and solidarity in front of the school where Paty worked, the College du Bois d’Aulnein in the suburb of Conflans-Sainte-Honorine.