JAPANESE SCHOOLGIRL, '15, BEATS UP FEMALE CLASSMATE TO DEATH AND THEN CHOPPED OFF HER HEAD AND HAND'.

In one of the most grisly crimes tackled by Japanese police, a schoolgirl has been arrested for strangling a classmate, severing her head and chopping off one of her hands.

Police who went to the 15-year-old high school girl's apartment in Sasebo, 900 miles south west of Tokyo, found the bedroom soaked in blood, with the decapitated body of her friend lying on the bed.

The 15-year-old suspect was being interviewed today to establish the reason for the alleged murder.

Police named the victim as Aiwa Matsuko, also 15, who died when she visited the accused schoolgirl's apartment in Sasebo, in Nagasaki Prefecture, 900 miles south west of Tokyo.

Police alleged that the suspect struck Matsuo on the back of the head more than 10 times with a blunt instrument and while she was unconscious strangled her.

Then as a final act, it is alleged, the suspect, who has not been named because she is a minor, cut off Matsuo's head and her left hand with a large knife.

The horrific crime came to light after Matsuo's parents contacted police to say their daughter had not returned home.

Police said Matsuo had earlier sent a message to her parents to say she was going to visit her friend at her apartment - then later sent her parents a text at around 7pm to say she was about to leave for home.

What had started out as a casual inquiry about a schoolgirl returning home late from a friend's house turned out to be an alleged investigation into one of the country's most shocking crimes in recent years.

Police found Matsuko's body lying on the suspect's blood-soaked bed. The knife and an unspecified 'blunt instrument' were lying nearby.

Officers said the two girls were alone in the apartment at the time of the crime. They alleged that the suspect, who did not live with her parents, admitted murdering her friend.

'She has not provided us with a motive for the attack at the moment,' said a police spokesman.

The victim had graduated from the same junior high school as the suspect.

The murder comes 10 years after Sasebo, with a population of 270,000, was rocked by the killing of a primary school girl who was stabbed by a classmate.