Dutch police said on Friday they had arrested a young woman in Rotterdam on suspicion of inciting threats, after a teacher went into hiding following a classroom discussion on the killing of French school teacher Samuel Paty last month.
It was not clear if the unidentified 18-year-old, who police said posted messages on social media, was a student at the Emmauscollege high school in Rotterdam.
Schools in the Netherlands, France and Germany had been asked to hold a moment of silence on Monday for Paty, who was beheaded by a man of Chechen origin in a Paris suburb last month after showing pupils cartoons of the Prophet Mohammad by the satirical magazine Charlie Hebdo.
During a classroom discussion at the Emmauscollege, students noticed a satirical cartoon that had been hanging on a bulletin board for years and some took offence.
The cartoon, which won a national prize in 2015, shows a decapitated figure labelled "Charlie Hebdo" sticking its tongue out at a bearded man with a bloody sword.
A photo of the image began circulating on social media and within a day the teacher had gone into hiding due to what police said were serious threats.
On Thursday a second school in Den Bosch said one of its teachers was staying home after a similar incident.
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The Rotterdam case was condemned by Dutch lawmakers and sparked a wider political debate.
"It is disturbing that our efforts to promote freedom of expression led to unrest and even threats at schools in Rotterdam and Den Bosch," Education Minister Arie Slob said in a letter to parliament.
"Intimidation of teachers cannot be tolerated in any way."