A mother and her boyfriend were arrested Thursday for allegedly injuring the woman's 8-year-old daughter by binding her wrists and forcing her into a cold bath at their home in southwestern Japan last month, police said.

The 29-year-old mother, whose name is being withheld to prevent the girl from being identified, and Jun Yahiro, 29, allegedly injured the daughter in the afternoon of Jan. 24 at their home in the city of Chikushino, Fukuoka Prefecture.

Yahiro, who lived with the two, is also suspected of hitting the girl several times around midnight that day, according to the police.

The woman and Yahiro have admitted to the allegations. The mother was quoted by the police as saying, "I did it to discipline her because she had wet the bed." Investigators suspect the girl may have been subject to daily abuse.

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A teacher at the girl's elementary school found bruises on her body on Jan. 25 and the school informed a local child welfare center, which took her into protective custody the same day and reported to police.

Child abuse cases in Japan have recently drawn the spotlight again after the death in January of a 10-year-old girl in Chiba Prefecture, near Tokyo, following alleged maltreatment by her parents, including food and sleep deprivation.

In March last year, the death of 5-year-old Yua Funato in Tokyo gripped the nation's attention as she had left desperate pleas for her parents to "forgive" her and stop mistreating her.

Prime Minister Shinzo Abe said earlier this month the government will confirm within a month the safety of all children suspected of being abused, as the Chiba case highlighted a lack of communication among authorities.