The women were forced into cars and raped in a "secluded area", police told BBC Hindi.
Police say they are investigating the incident but have not made any arrests.
The women were working with a non-governmental organisation (NGO) to raise awareness about human trafficking in the remote Khunti district.
About 40,000 rape cases were reported in India in 2016.
Many cases, however, are believed to go unreported because of the stigma that is attached to rape and sexual assault.