Police beat students with sticks in Kolkata on Monday (January 6) during a protest over a university attack in a different city.
That attack took place at a campus in Delhi on Sunday (January 5) and saw masked men burst in and attack students - leaving 30 in hospital.
New Delhi police are now investigating what happened.
It's the latest incident to ignite criticism of India's ruling Hindu nationalists.
The attack took place at a university long seen as a bastion of left-wing politics, and came as students nationwide lead a campaign against a citizenship law introduced last month by Prime Minister Narendra Modi that is seen as discriminating against Muslims.
Some have blamed the incident on a student union tied to Modi's Bharatiya Janata Party - though it has denied involvement.
(SOUNDBITE) (English) PROTESTER, SANGEETA, SAYING: "This is sick, where have we come to?
I mean, violence in universities, I cannot even imagine this.
I felt so safe when I was studying in college and what are we giving to our students, it is horrible, horrible, that's the least that I can say." Nearly a dozen students told Reuters that police failed to act, leaving them at the mercy of the mob.
The protests have persisted since the attack, with more demonstrations planned.