India's home minister says the government will conduct a national citizen survey to weed out those living illegally in the country.
Home Minister Amit Shah says people from all religions who can prove they are Indian citizens will be included in a National Register of Citizens.
Shah's announcement in Parliament on Wednesday came months after a mammoth survey in north-eastern Assam state, where about 1.9 million of the state's more than 32 million people were excluded from a registry as undocumented immigrants.
The state said those left out would have an opportunity to prove their citizenship at tribunals set up by the government.
Several political parties believe that many people, mostly Muslims, crossed illegally into India from neighboring Bangladesh.