"A landmark day for India and our nation's ethos of compassion and brotherhood! Glad that the #CAB2019 has been passed in the #RajyaSabha. Gratitude to all the MPs who voted in favour of the bill. This bill will alleviate the suffering of many who faced persecution for years," Prime Minister Narendra Modi tweeted soon after the Citizenship (Amendment) Bill was passed.

The Uddhav Thackeray-led Shiv Sena, which broke its alliance with the BJP in Maharashtra last month, walked out of the Rajya Sabha ahead of voting on the bill. The regional party had supported the legislation in the Lok Sabha, saying that it was in the "larger interests of the country".

Home Minister Amit Shah, tabling the bill in the Rajya Sabha, said Muslims of the country need not fear because "they are and will remain citizens of the country". Hitting out at what he called "attempts to spread misinformation", he claimed that the bill was only for minority communities in neighbouring countries and had "nothing to do" with Muslims in India.

The Congress's Anand Sharma made an impassioned plea against the bill, saying that it "hurts the very soul of the Constitution of India". "I am convinced this bill is an assault on the very foundation of the Constitution of India. It hurts the very soul of the Constitution of India. It goes against the very preamble of the constitution," he said.

Trinamool Congress MP Derek O'Brien warned the Rajya Sabha that India was "moving from a democracy to a dictatorship". In his address, Mr O'Brien invoked images from Nazi Germany and compared them to the Citizenship Bill and the NRC, starting with an "eerie similarity" between concentration camps and detention camps in the North East.

The BJP's JP Nadda rejected the opposition's claims that the Citizenship Bill was discriminatory. "That is absolutely incorrect," he said, stressing that the proposed law was "purely for minorities in Pakistan, Afghanistan and Bangladesh".

Congress MP P Chidambaram, out on bail in the INX Media case after a prolonged legal struggle, posed several key questions to the centre, including asking why only three of India's neighbours had been considered in the bill and why other communities and faiths - such as Sri Lankan Hindus - have been excluded.

Even as the Rajya Sabha debated the matter, the Army was deployed to parts of Tripura and Assam to quell protests against the bill. Despite Amit Shah's assurances that the Northeast won't be affected, protesters fear that the bill will steamroll the Assam Accord of 1985 and endanger the identity and livelihood of its indigenous population.

The Assam government has suspended mobile internet and data services in 10 districts of the state and imposed a curfew in Guwahati, the state's largest city. Guwahati has seen chaos of a magnitude not witnessed since the violent six-year movement by students that ended with the signing of the Assam Accord in 1985.