The incident occurred when the girl was alone in their rented house as other members of the family had gone to attend a function and the landlord along with four others gangraped her last evening.
The girl was found in a critical condition by her family when they returned and she was immediately taken to Amingaon Civil Hospital.
A case was filed this morning and four persons, including the landlord, were arrested, while the fifth accused was absconding.
The girl was later shifted to the Guwahati Medical College Hospital.