The police said the accused had threatened his daughter of dire consequences if she revealed anything to her mother.
"The victim finally told her mother yesterday that her father used to rape her when she used to go out for work. The mother did not immediately confront her husband and instead waited through the night and approached the police today," a senior police officer said.
Police arrested the father and have sent the victim for medical examination.
In another case, a four-year-old girl was allegedly raped by a juvenile in Anand Parbat area.
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The juvenile was caught red-handed by the girl's family members who rushed to the spot after hearing her cries for help, a police official said.
The juvenile, a school dropout, has been sent to a correction home for boys.
The Delhi Police have registered a case of rape and other relevant sections of Prevention of Children against Sexual Offences (POCSO) Act at the Anand Parbat police station.