Gérald 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 the Charlie Hebdo satirical magazine, where 12 people were gunned down for publishing the Mohammed cartoons.
The raids came a day after tens of thousands of people took part in rallies countrywide to honour slain history teacher Samuel Paty and to defend freedom of expression.
Police have detained 11 people over Friday's attack near the school where 47-year-old Paty taught in Conflans-Saint-Honorine, a usually quiet suburb around 30 kilometres northwest of central Paris.
The assailant, an 18-year-old of Chechen origin, was shot by police and later died of his injuries.
At the beginning of October, Paty taught a class on freedom of expression for which he showed pupils caricatures of the prophet Mohammed.
Police are investigating the role of a father of a schoolgirl and a known Islamist militant currently held by police, who posted a video on social media where he called for a dismissal of Paty for showing the cartoons.
“They apparently launched a fatwa against the teacher,” minister Darmanin told Europe 1 radio of the two men, who are among those being held over the attack.
Pour le ministre, il faut lutter contre la haine en ligne “Ils ont manifestement lancé une fatwa contre ce professeur. Le gouvernement et le Parlement ont essayé de lutter contre la haine en ligne avec la loi Avia. Une loi refusée par le Conseil Constitutionnel #Europe1 pic.twitter.com/c5SRq1uVbp
— Europe 1 ??? (@Europe1) October 19, 2020