Videos from Delhi showed protesters clashing with police at several university campuses, and at a major police station, where demonstrators demanded the release of arrested students.
According to Indian media, protests also broke out Sunday at other universities across the country, including in Hyderabad and Varanasi, while videos showed police firing tear gas at protesters at Aligarh Muslim University in Uttar Pradesh.
Anger has been growing nationally over the Citizenship Amendment Bill (CAB), which was signed into law last week. The bill promises to fast-track citizenship for religious minorities, including Hindus, Sikhs, Buddhists, Jains, Parsis and Christians, from Afghanistan, Bangladesh and Pakistan who arrived before 2015.
But the exclusion of Muslims -- which Modi says is because they are not minorities in India's neighbors -- has raised concerns about the bill's constitutionality and the growing anti-Muslim rhetoric in India.
Many in Assam and Tripura, states in India's northeast, also fear that it could see large numbers of Hindus migrating to the region, outnumbering the region's 200 distinct indigenous groups and changing its religious and ethnic makeup.
There are around 16 million Hindus in Bangladesh alone, and naturalizing large numbers of immigrants could also greatly impact employment, government subsidies and education.
Indian Prime Minister Narendra Modi and his Bharatiya Janata Party (BJP) have described the CAB as a means of protecting vulnerable groups from persecution, but critics say the true target is India's minority Muslim population and that it risks undermining the country's secular constitution.
"Today marks a dark day in the constitutional history of India," Sonia Gandhi, president of the opposition Congress Party, said in a statement. "The passage of the citizenship amendment bill marks the victory of narrow-minded and bigoted forces over India's pluralism."
Another leading Congress figure, Rahul Gandhi, said last week the law was an attempt to "ethnically cleanse the Northeast. It is a criminal attack on the Northeast, their way of life and the idea of India."
Protests have been ongoing in Assam and Tripura since the bill was passed into law. A large military presence has been deployed to the region, where internet access has been cut off. On Friday, hundreds of people joined a hunger strike demanding the bill's withdrawal.
Critics of the CAB say it is another example of how Modi and his BJP party have pushed an agenda of Hindu nationalism onto secular India, a country of 1.3 billion people, at the expense of its Muslim population.
The bill comes months after Modi's government stripped the majority-Muslim state of Jammu and Kashmir of its autonomous status, essentially giving New Delhi more control over the region's affairs and enabling mass Hindu migration to the region.
That same month, nearly 2 million people in Assam were left off a controversial new National Register of Citizens, which critics feared could be used to justify religious discrimination against Muslims in the state.