The two sisters, aged 25 and 23, work for a real estate company in Marathahalli in Bangalore East.
In a separate incident a 19-year-old girl was allegedly gangraped twice by eight persons in the coastal town of Mangalore on December 25.
The incident came to light only on Thursday when the girl recorded her statement before the police.
The girl, belonging to a village in coastal Karnataka, works as a domestic help in Mangalore, police said. She is the sole bread-earner of her family of two — a younger brother and their mother.