The girl's family lives in a rented accommodation in the boy's house.
Police said the matter came to light late last night when the girl's mother noticed blood and injury marks on her body.
According to the police, the boy allegedly raped the girl, a Class I student, when she was alone in house.
The girl's father, who works in Noida, told police in his complaint that his landlord's son, a Class VIII student, took his daughter to the terrace on the pretext of flying a kite and allegedly raped her at around 7 PM.
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When the girl's mother came back home, she noticed that her daughter was bleeding and had injury marks on her body. She told her husband about the incident when he returned from work.
"The girl's father later registered a complaint at Vijay Nagar Police Station," said a senior police officer.
"We have sent the girl for medical examination.Police are investigating the case," the officer said.