Demonstrations have been called around France in support of freedom of speech and to pay tribute to a history teacher who was beheaded near Paris after discussing caricatures of Islam’s Prophet Mohammed with his class.

Samuel Paty 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 cities including Lyon, Toulouse, Strasbourg, Nantes, Marseille, Lille and Bordeaux.

The gatherings come as French authorities said they have detained a 10th person following the horrific attack in Conflans-Sainte-Honorine, north-west 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, 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 provoked global condemnation.

US President Donald Trump referred to the killing on Saturday night during a political rally in Janesville, Wisconsin.

“On behalf of the United States, I’d like to extend my really sincere condolences to a friend of mine, President (Emmanuel) Macron of France, where they just yesterday had a vicious, vicious Islamic terrorist attack – beheading an innocent teacher near Paris,” he said. “France is having a hard time and Macron’s a great guy.”

Read more: Suspect in French beheading horror was Chechen teenager