Nine people were killed and 65 injured on Tuesday in Tamil Nadu after police opened fire at protesters in Thoothukudi, who had been seeking a ban on Sterlite Industries' copper plant.
The protesters, who launched their protest many months ago, accuse Sterlite Industries of releasing pollutants from its plants and have been demanding the plant be closed.
A judicial inquiry has been ordered into the incident by Tamil Nadu's Chief Minister Edappadi K Palaniswami
The ruling AIADMK government has been widely criticised for the incident.
Rahul Gandhi said the police's actions were "state sponsored terrorism".