In 1978, observers noticed the names of an estimated 45,000 Bengali illegal immigrants on the electoral rolls in Assam. This led to a popular movement against undocumented immigrants known as the Assam Movement, which insisted on striking the names of illegal immigrants from the electoral register and advocated for their deportation from the state. The movement demanded that anyone who had entered the state illegally since 1951 be deported, though the central government insisted on a cutoff date of 1971. There was widespread support for the movement, though it tapered off between 1981 and 1982.

Toward the end of 1982 the central government called elections, and the Assam Movement called for people to boycott them. This resulted in the 1983 Nellie massacre, described by Antara Datta, as one of the largest and most severe pogroms since the Second World War. Previously, the All Assam Students Union (AASU) had emphasised economic reasons for the protests and had employed only nonviolent methods. The Nellie massacre, a result of a buildup of resentment over immigration, claimed the lives of at least 2,191 people, though unofficial figures run to more than 5,000. No investigation of the incident has ever been launched. The AASU denied any involvement in the massacre, and since then there have been no instances of communal violence in Upper Assam.

On 26 April 2015 at a rally in Guwahati BJP National president Amit Shah said that BJP government will give citizenship to all Hindu immigrants who had to flee from Bangladesh due to religious persecution.

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