A 29-year-old Nagasaki man was arrested Monday on suspicion of pouring boiling water over the 6-year-old son of a woman he lives with, police said.

According to police, Tetsuji Oyama bound the boy's hands with a towel in mid-July and poured boiling water from a pot onto him. The child sustained burns to his chest and shoulders.

The suspect has essentially owned up to the allegations, police said. Child welfare authorities had been looking into the boy's case since late June, as neighbors alerted the boy's elementary school that he was acting strangely and had bruises on his body, police said.

According to the local child welfare office, the boy had bruises and burn marks on his body. He has been placed in the care of a welfare facility.

The boy's 26-year-old mother was quoted as telling welfare officials that she was too frightened of Oyama to stop him from hurting her son, police sources said.

Investigators were continuing to question the suspect to establish a clear motive for the abuse, they added.