Two accused, including a minor have been nabbed in connection with the case, police said.
The girls have been admitted to the Baba Bhim Rao Ambedkar hospital where the condition of one of them is critical.
The incident happened this afternoon when the girls went to attend the nature's call in a vacant place near their home in Rohini Sector 26. Both of them are neighbours and had returned from school.
The accused were nabbed from the area later and are being interrogated.