The alleged crime took place four days ago and it was reported to the police yesterday.
The accused lived on the second floor of a building, while the victim lived on the third floor along with her family, the police said.
The accused allegedly lured the girl on the pretext of playing with her and then sexually assaulted her, they added.
The girl was in a state of shock after the incident. She stopped talking to her family members and kept to herself. When her mother inquired about this change in her behaviour, she broke down and narrated her ordeal.