Police arrested nine people on charges of murdering Jivan Kohar, son of Shiv Sharan Kohar of Kudiya village in Nawalparasi district which borders India.
During police interrogation, the main accused Kodai Harijan confessed that he sacrificed the boy, son of his friend Kohar, by slitting his throat to chase away the evil spirits from the body of his ailing son.
Kodai gave Rs 50,000 to people who assisted him in the crime. He said he felt guilty now, but did it to cure his son.
The victim was playing at his neighbour's house as his family members had gone to field.
The boy, who had gone missing since Tuesday, was found dead with his throat slit in a bush near Shiwan temple on the bank of the Patera river on Thursday, police said.