Kumar, Umar Khalid and 18 others began their hunger strike late Wednesday night and said they rejected the findings and recommendations of the high-level inquiry committee that probed the February 9 event on the campus here.
"From the very beginning, we've maintained that we have no faith in the inquiry committee. The inquiry was a sham and we will not accept the punishment given to us," Kumar said while addressing students in the JNU campus.
Earlier on Wednesday night, the protestors also took out a march from the Ganga Dhaba to the administrative block on the campus.
Jawaharlal Nehru University's five-member inquiry committee had on Monday fined Kumar Rs.10,000 and rusticated students Umar Khalid, Anirban Bhattacharya and Mujeeb Gatto.
The committee, constituted on February 11, ordered the rustication of Bhattacharya till July 15 and barred him from the university from July 25 for five years. He can submit his Ph.D. during the July 15-25 period.
Bhattacharya and Khalid will lose a semester of their academic session while Gattoo has been suspended for two semesters, an order from the university proctor said. Khalid also must cough up Rs.20,000 as fine by May 13.
Also fined varying amounts were 10 other students, including one from the Akhil Bharatiya Vidyarathi Parishad, on charges of obstructing traffic on the campus.
Anti-national slogans were raised at an event held on the JNU campus on February 9 to commemorate executed parliament attack convict Afzal Guru, following which Kumar, Khalid and Bhattacharya were arrested on sedition charges.