The culprit, Honey Othwal (18), the son of the victim's paternal uncle, was subsequently arrested by the police yesterday at Malhargarh town, about 25 kms from here, in Mandsaur.
During interrogation, Honey told the police that he committed the offence yesterday in an inebriated condition and then threw the victim's body in a water tank after throttling her to death.
The victim had come from Mandsaur to Malhargarh to spend time with her grandparents when the offence took place.
The post mortem of the deceased established rape, police said, adding that that the accused would be booked under relevant sections of IPC.