French police on Monday raided the homes of dozens of suspected Islamist terrorists three days after the beheading of a teacher who had shown his pupils cartoons of the Prophet Mohammed, the interior minister said.

The raids came a day after tens of thousands of people took part in rallies countrywide to honour teacher Samuel Paty and to defend freedom of expression.

Gerald Darmanin said the swoop on Islamist networks was designed to send a message that “enemies of the Republic” would not enjoy “a minute’s respite”.

He said over 80 investigations had been launched for online hate speech following the attack, which has drawn parallels with the 2015 massacre at Charlie Hebdo satirical magazine, where 12 people were gunned down for publishing the Mohammed cartoons.

That attack -- the first in a string of assaults that have killed over 240 people in France -- brought over a million people onto the streets of Paris to denounce extremism.

On Sunday, people again congregated on Place de la Republique in Paris, where world leaders had marched alongside the French in 2015.

Some in the crowd chanted “I am Samuel”, echoing the 2015 “I am Charlie” rallying call by supporters of free speech.

Paty, 47, was murdered on his way home from the school where he taught in a suburb northwest of Paris on Friday afternoon.

A photo of the teacher and a message confessing to his murder was found on the mobile phone of his killer, an 18-year-old Chechen man Abdullakh Anzorov, who was shot dead by police.

Eleven people are being held over the attack, including a known Islamist terrorist and the father of one of Paty’s pupils who had railed against him online and called for his dismissal.

Darmanin accused the two men of having issued a “fatwa” against Paty, using the term for an Islamic edict that was famously used to describe the 1989 death sentence handed down against writer Salman Rushdie by Iran’s Ayatollah Khomeini.

“They apparently launched a fatwa against the teacher,” the minister told Europe 1 radio.

Anzorov’s family arrived in France when he was six from the predominantly Muslim Russian republic of Chechnya.