Teachers, a pulp thriller, and internet chat are all being accused of contributing to the killing of an elementary schoolgirl by an 11-year-old classmate in Japan.

Child A, who cannot be named under Japanese law, was taken into custody last week for cutting the throat of 12-year-old Satomi Mitarai with a craft knife which she carried in her pencil case.

Confessions given to investigators have revealed a motive based on mildly venomous bickering via the school’s instant messaging board and a school-based horror novel as inspiration for the attack.

Since Satomi’s death commentators have questioned the vigilance of teachers at the Okubu elementary school in Sasebo, Nagasaki, where the attack took place in an empty classroom at lunchtime last Tuesday. According to media reports, the killer’s fellow pupils were aware of child A’s erratic behaviour prior to the murder.

Students spoke of her constant “flaming” (vitriolic put-downs) of other students via the school’s internet site, targeting her victim, with whom she had fallen out weeks before.

Child A also posted a short story on the site, based on an infamous novel, Battle Royale - Whisper, in which children in a junior high class are transported to a desert island and forced to kill each other until only one girl remains. The book was the basis for a gory cult thriller, Battle Royale, in 2000. Directed by the late Kinji Fukasaku, it attracted more than 1.8 million fans in Japan but its violence outraged teachers.

A worrying sign for schools worldwide is that charges were laid last week in three other copy-cat cases of school murder plots in Japan, Sweden and the United States (see below). They were based on either Battle Royale or the real-life Colombine high-school massacre in which two pupils killed 12 classmates, one teacher and themselves in Colorado in 1999.

In the wake of the press revelations Okubu school officials said they were discussing ways to prevent a recurrence and reviewing student supervision guidelines.

Education officials in Nagasaki have also announced that the city will now carry out a survey of the use of internet chat rooms by primary and middle school students.

Superintendent of municipal education for Sasebo, Koichi Tsurusaki, told the Daily Yomiuri newspaper: “We must confirm whether schools have taught students about the dangers of violating the rights of others. We need to put together rules on communicating on the internet.”

Teachers have been blamed in the past for being far less internet aware than their techno-savvy charges. Nearly every child in Japan carries an internet-enabled phone. Almost all schools have access to the web and government data shows that more than 60 per cent of children aged between six and 12 use the internet.

Sociology professor and education expert at Tokyo University Michio Nitta told The TES that the mass-media had been too quick to scapegoat publishers, the internet and teachers.

“Attacking teachers and parents will do more harm than solving the problem.

And even we do not know what is the problem is.

“It’s difficult to understand this kind of event by just reading answers of an 11-year-old girl. We will have to wait for a report of expert psychologists or psychiatrists who will be given a chance to make lengthy interviews.”

Child A’s lawyers say she is answering questions perfectly calmly and needs no psychiatrist, according to media reports.