Children aged 15 and below underwent sterilization under Japan's now-defunct 1948 eugenic protection law in at least 13 of 47 prefectures due to mental disabilities and other reasons, a Kyodo News tally showed Wednesday.

The latest findings, which show the youngest such child was aged 9, raise suspicions that sterilization may have been forced on young girls who had no possibility of becoming pregnant in suspected deviation of a subsequent state notification attached to the law.

"It would be surprising if such sterilization was implemented widely," Keiko Toshimitsu, a visiting bioethics researcher at a Ritsumeikan University research center, said, referring to the 1953 notification that had limited the forcible removal of reproductive organs only to cases where "there is a possibility of bearing a baby."

"Girls would have had to undergo abdominal surgeries, which are a great physical burden. I suspect that the operations were conducted based on extreme discrimination and prejudice," she added.

While the controversial law was scrapped in 1996 and replaced by the maternal protection law on abortion, the perceived human rights infringement through the eugenic law has drawn renewed attention recently, as in the case of a lawsuit filed by a woman seeking compensation from the state over her forced sterilization when she was a teenager.

According to the Kyodo News tally, papers listing individual names of people who are believed to have been subjected to sterilization were found in 23 prefectures. So far, there are records of 3,400 men and women.

Of the 23 prefectures, 13 have kept documents showing children aged 15 or younger were subjected to sterilization, with the youngest being a 9-year-old whose case was screened in Miyagi Prefecture and the oldest one a 57-year-old of a case in Saitama Prefecture.

The documents also showed there were 11-year-olds in Hokkaido and Chiba, 12-year-olds in Yamagata, Kanagawa, Gifu and Kyoto, and 13-year-olds in Fukushima, Mie, Nara and Hiroshima.

The eugenic protection law authorized the sterilization of people with mental disabilities and illness or hereditary disorders to prevent births of "inferior" offspring. It also allowed for forcible abortions without the consent of the individuals or their relatives.

In 2016, the U.N. Committee on the Elimination of Discrimination against Women recommended that Japan adopt "specific measures aimed at providing all victims of forced sterilizations with assistance to access legal remedies and provide them with compensation and rehabilitative services."