The incident occurred on December 23 when the girl had gone to the field for farming work. The Class 8 student's lifeless body was found lying in a ditch next to a field on Saturday, Namsai Deputy Commissioner R K Sharma said.
"The perpetrators of such a heinous crime should be immediately nabbed and given exemplary punishment," the chief minister condemned the act and also sought immediate action against the accused.
Expressing deep sorrow over the unfortunate incident, Mr Khandu announced an ex-gratia of Rs 4 lakh for the next of kin of the minor girl. He also directed the district administration and the police to intensify the investigation and ensure justice at the earliest so that the people are able to restore their faith in the public administration and the police.
Deputy Chief Minister Chowna Mein too conveyed his anguish over the incident and termed it as "shameful and worrying."
Many societies have come out to protest against the heinous crime and have also vowed to stand by the girl's family.
(With inputs from PTI)