The Citizenship Amendment Bill was passed by a majority vote in India's lower house after midnight and still needs to be passed by upper house before becoming law.

The shutdown began at 5 a.m. and was organized by the North East Students Organization, an association of student groups from across India's eight northeastern states. They oppose the bill out of concern that more migrants will move to the border region and dilute the culture and political sway of indigenous tribal people.

"The northeast is already hit by large scale illegal influx from Bangladesh and now the government is trying to provide citizenship to a whole lot of migrant Hindus and others. How can you grant citizenship on the basis of religion?" said Samujjal Bhattacharya, a leader of the All Assam Students Union.

Protesters blocked traffic across the state of Assam, including in the state capital Gauhati, by burning tires and sitting on roads. Shops and businesses closed, and several vehicles were vandalized.

The protesters have burned effigies of leaders of the ruling Bharatiya Janata Party including Prime Minister Narendra Modi, Home Minister Amit Shah and Assam Chief Minister Sarbananda Sonowal.

Bhaskar Mahanta, Assam's police chief, said that several protesters had been detained or arrested, but the situation was under control.

The bill was first introduced by the Modi government in Parliament earlier this year, but stalled in the upper house because of wide-scale protests in India's northeast.