The Jawaharlal Nehru University administration said students agitating over the hike in hostel fees "ransacked" the server room and "intimidated" the technical staff on Saturday, hampering the semester registration process.
But JNUSU said the administration used "masked" security guards to attack students. "They were shamefully wearing masks. JNUSU president was openly slapped by one of the security guards," alleged the students' union, which has called for a boycott of the process over the increase in hostel fees.
The semester registration process will end on January 5.
The university has been seeing a standoff between the students and the administration over hike in hostel fees for over 70 days. Students even boycotted exams in protest, prompting the administration to send question papers to students through WhatsApp and email, a move condemned by the union.
Explaining the events, the university said the technical staff gained access to the communication and information services (CIS) premises Saturday morning, after the servers were made dysfunctional by students on Friday, with the help of security guards and rebooted the servers, the university said.
But a group of "miscreants" entered the server room, intimidated the staff, and damaged the systems around 1pm, it alleged.
Around 4pm, the staff once again gained access to the CIS room and were trying to restore the systems.
Appealing to students to continue the boycott of the registration process, the JNUSU claimed the administration is "extremely rattled" by the unity of students.
Meanwhile, the RSS-affiliated Akhil Bharatiya Vidyarthi Parishad said its members protested against the disruption of internet, after which they were attacked by the members of the Left Unity.
The JNUSU alleged that students were attacked by ABVP members.
JNU Teachers' Association condemned the incidents of violence at the university.
"While condemning the violence and appealing to all to maintain peace and preserve the democratic culture of the University, the JNUTA notes the dubious role of the JNU administration whose acts of commission and omission are chiefly responsible for creating this situation," it said.
Instead of discharging its responsibility to prevent violence, the administration appears to be going down the "dangerous path" of provoking and encouraging it, it added.
A varsity official said they have given police complaints in connection with the action of the students.
The university said it will make every attempt to help students register for the winter semester and continue their academic pursuits. "The university has also announced an alternate way of registering for the winter semester to make it easy for the students to register," it said in a statement.
According to university registrar Pramod Kumar, they will make the entire registration process online so that students will not have to visit the schools to take the signatures of the deans.
Officials said since the servers have been left disarray, it might take time to restore them and the varsity is mulling to extend the registration deadline. However, a final decision is yet to be taken.
"The agitating students cannot trample upon the fundamental rights of the rest of the student community to pursue their studies. Such hooliganism and uncivilised behaviour by them has seriously affected the image of the university," the varsity said.
The administration appealed to the student community not to be misled by the agitators and their advisers, who are trying to "derail the normal functioning of the university through their unlawful actions".