A teenage girl arrested over a random attack with a knife in Tokyo's Shibuya district has said she stabbed two people she came across because she "wanted to get the death penalty," the police said Sunday.

The girl, who was arrested Saturday on the spot on suspicion of attempted murder, has been identified as a 15-year-old junior high school student from Toda, Saitama Prefecture, north of Tokyo. Her name has been withheld because she is a minor.

The girl is suspected of stabbing a 53-year-old woman and her daughter, 19, from behind at around 7:20 p.m. with a kitchen knife on a street in Maruyama-cho, Shibuya Ward, near Shibuya Station.

Photo shows the area near the scene of the stabbing of a mother and daughter in Tokyo's Shibuya Ward on Aug. 20, 2022. (Kyodo)

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The Metropolitan Police Department has seized three small knives the girl was in possession of at the time of the attack.

The mother and daughter suffered serious injuries requiring at least three months to heal, with the daughter sustaining a stab wound to her back more than 10 centimeters deep, the police said.

The girl denied the attack was linked to any trouble at home or school, according to the police, who did not elaborate further on motive.

But she did say that she wanted to do a practice run to see if she was capable of killing a person as she had plans to kill her mother, according to investigative sources.

After leaving her home around noon on Saturday, she got off at Shinjuku Station and walked toward the scene of the attack.

A witness told Kyodo News that when the girl was held down by police officers, she was crying quietly with knives scattered around her. Wearing pants and a T-shirt, which had blood on it, the girl "had black hair and looked young," the 28-year-old man said.