An eerie silence descended over the Aligarh Muslim University campus on Thursday even as hundreds of student protesters gathered at the Baab-e-Syed gate, the scene of Wednesday's violent incident in which around 20 students were injured in police action.

Violence broke out at the Aligarh Muslim University on Wednesday after rightwing protesters barged into the university, demanding removal of the portrait of Muhammad Ali Jinnah displayed on the campus.

Following Wednesday's incident, policemen in large numbers and a RAF contingent were deployed near the Baab-e-Syed gate to maintain law and order.

While the rest of the injured students were discharged after receiving first aid, three of those with serious injuries are admitted at the Jawaharlal Nehru Medical College hospital.

According to a hospital official, all the three students are out of danger and recovering.

On Thursday, the AMU students sat on an indefinite dharna demanding action against the protesters.

The AMU Students' Union (AMUSU) alleged that violence on the campus was a "deliberate and pre-planned attempt" to attack former vice president Hamid Ansari, who was at that time barely 100 metres away at the university guest house, from where the violence erupted.

"Our protest will continue indefinitely till the police takes action against those who were actually targeting the former vice president who had come to the AMU where he was to be granted a lifetime membership of the Students' Union," AMUSU said in a statement issued here.

President, AMUSU, Mashkoor Ahmad Usmani, who was also injured in Wednesday's lathicharge by the police, said the students would approach the National Human Right Commission "with the help of all secular organisations of the country" if all doors to justice are closed by the state government.

A spokesman of the varsity strongly condemned Wednesday's "trespassing" of the university boundary by Hindu Yuva Vahini (HYV) activists who were raising "highly objectionable and inflammatory slogans." The HYV was founded by present UP Chief Minister Yogi Adityanath and has been perceived as becoming more brazen in its approach since Adityanath assumed office last year.

"We hope that the state government will take strong action against the Hindu Yuva Vahini youths who deliberately tried to disturb peace on the university campus," he said.

The AMU Teachers' Association (AMUTA) held an emergency meeting on Wednesday night and passed a resolution stating that the action by the HYV was a "deliberate criminal conspiracy" in which the police instead of punishing the aggressors, indulged in "brutal action" against the students, who had later collected at the gate to protest the failure of the police to prevent the outsiders from entering the campus.

It has demanded that an FIR should be lodged against those who "masterminded the entire operation."

The AMUTA blamed the police for its "glaring security breach" for allowing "armed goons" to reach a spot that was just adjoining the university guest house where the former vice president was staying.