India's ruling Hindu nationalist government on Wednesday won parliamentary approval for a far-reaching citizenship law that critics say undermines the country's secular constitution, as protests against the legislation intensified.
The Citizenship Amendment Bill seeks to grant Indian nationality to Buddhists, Christians, Hindus, Jains, Parsis and Sikhs who fled Afghanistan, Bangladesh and Pakistan before 2015.
The bill passed the upper house of parliament with 125 members supporting it and 105 opposing.
The move by Prime Minister Narendra Modi's government faced stiff resistance from opposition parties, minority groups and student bodies, with some calling it discriminatory against Muslims.
It is the third key election promise that Modi’s government has delivered since he was re-elected in August, re-energising his nationalist, Hindu support base and drawing attention away from a slackening economy.
As the upper chamber debated the bill, demonstrations against it turned violent in the country's ethnically diverse northeast.
Soldiers were deployed in Tripura state and reinforcements put on standby in neighbouring Assam, both of which border Bangladesh.
Despite assurances from India's Home Minister Amit Shah that safeguards will be put in place, people in Assam and surrounding states fear that an influx of settlers could lead to a competition for land and upset the region's demographic balance.
Some opposition Muslim politicians have also argued that the bill targets their community, which numbers more than 170 million people and is by far India's largest minority group.
The government has said the new law will be followed by a citizenship register that means Muslims will have to prove they were original residents of India and not refugees from these three countries, potentially rendering some of them stateless.
The US Commission on International Religious Freedom said on Monday that Washington should consider sanctions against Shah, a close associate of Modi, if India adopts the legislation.
"The passage of the Citizenship Amendment Bill marks the victory of narrow-minded and bigoted forces over India’s pluralism," said Sonia Gandhi, leader of the main opposition Congress party.
Defending the bill in the upper house, Shah said the new law only sought to help minorities persecuted in Muslim-majority countries contiguous with India.
"Nobody is taking citizenship away from India's Muslims. This is a bill to give citizenship, not take citizenship away," Shah said.
In another move criticised by Muslims as discriminatory, the government scrapped the disputed Kashmir region's autonomy.
Last month, the country's supreme court also allowed the construction of a Hindu temple at a religious site in Northern India also claimed by Muslims.
A curfew has been imposed in Assam's main city of Guwahati after police clashed with thousands of protesters, beating them back using water cannons and tear gas.
State authorities in Assam also blocked mobile internet services in 10 districts, fearing further violence.
Protesters, many of them students, remained on the streets late into Wednesday evening, where bonfires were lit, public property vandalised and vehicles set on fire.
"The bill will take away our rights, language and culture with millions of Bangladeshis getting citizenship," said Gitimoni Dutta, a college student at the protest.