Violent clashes erupted in Delhi between police and hundreds of university students on Friday over the enactment of a new citizenship law that critics say undermines India's secular foundations.
The unrest has already led Japanese Prime Minister Shinzo Abe to cancel a planned visit to India from Sunday.
The new law offers a way to Indian citizenship for six minority religious groups from neighbouring Bangladesh, Pakistan and Afghanistan including Hindus and Christians, but not Muslims.
Police fired tear gas and used baton charges to disperse scores of students demonstrating at Jamia Millia Islamia university in the heart of Delhi over the law.
Protesters attacked cars in the capital, and several people were injured and taken to hospital.
Zakir Riyaz, a PhD student in social work, said the new law made a mockery of India's religious openness.
"It goes against the whole idea of a secular India," he said, speaking by phone from the Holy Family Hospital in New Delhi where 15 of his fellow students were admitted after being injured in a police baton charge.
Police barricades were knocked down and streets were strewn with shoes and broken bricks. An official at the university dispensary said that more than 100 students had been brought in with injuries but all had been discharged.
Parvez Hashmi, a local politician who went to the protest site to speak to police, said about 50 students had been detained.
Students said it was meant to be a peaceful protest, with them trying to go from Jamia University to Parliament Street to show their opposition to the legislation. But police pushed them back, leading to clashes.
Critics of Prime Minister Narendra Modi's government say it is promoting a Hindu-first agenda for India and that the citizenship law excluding Muslims showed a deep-seated bias against India's 170 million Muslims.
Imran Chowdhury, a researcher, said "either give citizenship to refugees of all religions or none at all. The constitution is being tampered with in the name of religion."
Modi's ruling Bharatiya Janata Party denies any religious bias but says it is opposed to the appeasement of one community. It says the new law is meant to help minority groups facing persecution in the three nearby Muslim countries.
The United Nations human rights office voiced concern that the new law is "fundamentally discriminatory in nature", and called for it to be reviewed.
Two people were killed in India's Assam state on Thursday when police opened fire on mobs torching buildings and attacking railway stations in protest at the new citizenship rules signed into law on Thursday.
Japan's Prime Minister Shinzo Abe cancelled a trip to Assam for a summit with his Indian counterpart Narendra Modi that had been due to begin on Sunday.
Japan has stepped up infrastructure development work in Assam in recent years, which the two sides were expected to highlight during the summit. Abe had also planned to visit a memorial in the nearby state of Manipur where Japanese soldiers were killed in World War Two.
"With reference to the proposed visit of Japanese PM @AbeShinzo to India, both sides have decided to defer the visit to a mutually convenient date in the near future," Indian foreign ministry spokesman Raveesh Kumar said in a tweet.
Japan's Chief Cabinet Secretary Yoshihide Suga said both countries would decide on the appropriate timing for the visit although nothing has been decided yet.
A movement against immigrants from Bangladesh has raged in Assam for decades. Protesters there say granting Indian nationality to more people will further strain the state's resources and lead to the marginalisation of indigenous communities.