The incident came to light on Wednesday afternoon when the girl complained of pain in her abdomen. She later told her parents that she was being allegedly raped by her 13-year-old friend, who lives in the same neighbourhood, for many days.
"The juvenile stays with his parents in a rented apartment in Govind Puri and studies in class 7 in a government school. He was caught from his residence soon after the victim's parents filed a complaint against him," a police officer said.
During investigation, it was found that the boy would enter the girl's house on the pretext of playing with her after her parents would leave for work and then allegedly rape her, the officer said.
"She has been admitted to Safdarjung Hospital and her statement will be recorded on Friday."
The girl's father (name withheld to protect the victim's identity) told IANS: "I work in a hotel and my wife works in a factory. We both go for work leaving our two daughters and a son under the observation of their ailing grandfather who cannot walk properly."
"The grandfather used to take rest on a cot outside the house. The boy entered our house on the pretext of playing and raped her whenever he found her alone," he said.
The boy has been sent to a juvenile home, police said.