French police on Monday launched a series of raids targeting Islamist networks, three days after a history teacher who had shown his pupils a cartoon of the Prophet Mohammed was beheaded in a suburb of Paris.
Interior Minister Gerald Darmanin vowed there would be "not a minute's respite for enemies of the Republic", after tens of thousands took part in rallies countrywide on Sunday to honor the teacher, Samuel Paty, and defend freedom of expression, according to AFP.
15 people have been detained so far, including four pupils who may have helped the killer -- an 18-year-old of Chechen origin who was killed by police -- to identify the teacher in return for payment.
Law enforcement carried out 40 raids on Monday, mostly around Paris, with many more planned, AFP reported.
"We want to harass and destabilize this movement in a very determined way," one ministry source said.
Darmanin said the government would also tighten its grip on institutions and charities with suspected links to Islamist networks.
Paty, 47, was attacked as he was making his way home from the junior high school where he taught in Conflans-Sainte-Honorine, located 40 kilometers (25 miles) northwest of Paris.
A photo of the teacher and a message confessing to his murder was found on the mobile phone of his killer, Abdullakh Anzorov, who arrived in France with his family from the predominantly Muslim Russian region of Chechnya more than a decade ago.
Four members of the killer's family are among those detained by the police.
Paty had shown his civics class one of the controversial cartoons of the Prophet Mohammed after first giving Muslim children the option to leave the classroom, but the lesson nonetheless caused uproar.
The father of one of Paty's pupils launched an online campaign against the teacher and has now been arrested along with a known Islamist radical, according to AFP.
Officials named two groups they would target for closure -- the Collective Against Islamophobia in France that claims to monitor attacks against Muslims and BarakaCity, which describes itself as a humanitarian organization.
Darmanin also ordered the closure of a mosque in the Parisian suburb of Pantin, accusing its imam of encouraging intimidation of the teacher and publicizing the address of the school.
In recent years, France has been hit by a number of attacks claimed by ISIS, the biggest one being the attack in November of 2015 in which 129 people were murdered.
The country has been under a heightened alert in recent years in the wake of the attacks.
Just last month, a 25-year-old man wounded two people in a meat cleaver attack in Paris. He was subsequently charged with "attempted murder with relation to a terrorist enterprise."