Police have arrested the father-son duo and also taken parents of the girls into custody for questioning. The victims are aged eight and 10 years.
The victim’s 13-year-old brother and some others were also being questioned by the police for their alleged involvement in what is being suspected as a child sex abuse racket.
Police suspect that the parents of the girls knew about the abuse going on at their house in Mylardevpalli, a locality on the southern fringes of the city.
The sordid story came to light on Friday after one of the girls complained of stomach pain and their school teacher alerted a child rights organisation.
The police have arrested Jaffar (40) and his minor son on charges of rape, intimidation and under various sections of Protection of Children from Sexual Offences (POCSO) Act.
Jaffer reportedly developed friendship with the victims’ mother and was sexually abusing the sisters with her help.
The victims’ mother is a security guard in a private firm, and their father works at a factory. The family originally hails from Uttar Pradesh and were living here for last 16 years.
A friend of the main accused, minor brother of the girls and his friend were also suspected to be involved.
Authorities had sent the victims for medical examination. They were later shifted to a rescue home for counselling and rehabilitation. Officials said the minor girls were in a state of shock.
Balala Hakkula Sangham (BHS), the organisation working for protection of child rights, said the parents were involved in the crime. The BHS demanded that the authorities ask the couple to prove that they are the biological parents of the victims.
BHS President Anuradha Rao suspects it to be a child trafficking racket. She said only a through probe could unravel all the details of the crime.