The National Police Agency said Thursday that 56 children died as a result of child abuse in the 12 months after a law against abuse came into force in November 2000.
The figure marked an increase of 13 children, or 30 percent, compared with the same period the previous year.
Assault was the cause of 25 of the deaths, 22 children were murdered, six died as a result of guardians abandoning their responsibilities, and the remaining three died of other forms of negligence.
"The child abuse situation remains serious," agency officials said. "We intend to strengthen our work with relevant agencies in order to promote quick detection of child abuse."
The new law gives child-welfare authorities the power to take temporary custody of children from abusive parents and allows them to enter the home of guardians implicated in child abuse to investigate. Parents who refuse to cooperate are subject to fines of up to 200,000 yen. The law also obliges citizens who discover any abuse cases to notify authorities.
The NPA said 186 cases of child abuse were reported to police nationwide during the 12-month period under review, eight more than the previous year.
The number of children involved amounted to 192, up by 10 from the previous year, and police filed charges against 211 people, 12 more than the previous year.
The agency said 131 cases of child abuse reported to police over the 12-month period involved physical assault, 33 cases involved sexual abuse and 22 cases involved negligence including denying food to children.
Mothers made up the largest number of child abusers at 79, followed by 44 live-in partners of the child's father or mother and 33 stepfathers or foster-fathers.
Of the abused children, 37 were under 1 year old -- making up the largest age group of victims -- 18 were 1-year-olds and 20 were between 2 and 3 years old. Preschoolers comprised 62 percent of the total.