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A student has been arrested in JapanReuters

A 15-year-old Japanese student has been arrested on suspicion of killing a classmate, according to police in Japan.

The suspect is accused of striking 15-year-old student Aiwa Matsuo on the back of her head more than 10 times with a blunt instrument and strangling her.

Police said the teenager's head was severed with a knife and her left hand was chopped off.

Matsuo was said to be visiting the suspect at her home in Sasebo, Nagasaki, when the attack took place, Japan Today reported.

The suspect, who cannot be named for legal reasons, was arrested after she allegedly confessed to the crime.

The suspect said: "I did it all by myself," Kyodo news agency reported.

The victim was found dead on a bed in the suspect's apartment early on Sunday. Both went to the same senior high school, said the agency.

"I feel so sad and frustrated," said the principal of the high school. "We have kept calling attention to the value of life but the message has not been delivered." 

The incident has sent shockwaves through the teaching community in Sasebo; it had been rocked by an episode in 2004 when a primary school girl killed her classmate.