Hundreds of teachers at one of India's top universities went on strike Tuesday to protest the arrest of a student on a controversial sedition charge that has sparked mass protests, an activist said.

Student union leader Kanhaiya Kumar was arrested on Friday for allegedly shouting anti-India slogans at a rally in protest against a Kashmiri separatist's execution three years ago.

Kumar, head of the student union at New Delhi's prestigious Jawaharlal Nehru University (JNU), was remanded in custody on Monday at a hearing marked by violent scuffles outside the court where fellow students and journalists had gathered to witness his appearance.

His arrest has fed into a row over freedom of expression in India, where some rights campaigners say the Hindu nationalist government is using the British-era sedition law to clamp down on dissent. Sedition carries a maximum penalty of life imprisonment in India.

Students at JNU said Monday they would boycott classes until Kumar is released, after staging major protests at the weekend.

On Tuesday they were joined by hundreds of teachers at the university, which has a long history of left-wing activism.

"The teachers went on strike today. Some 500 teachers have gathered near the university's administrative block with banners to show their solidarity with the students," said Om Prasad of the All India Students Association.

"They are demanding the immediate release of Kanhaiya and withdrawal of all the cases," he told AFP.

JNU faculty member Rohith Azad, who was among those targeted at the court on Monday, said the university was being "openly attacked".

"The entire world is now referring to JNU as a hub of anti-nationals on (the) basis of propaganda," the teacher told The Hindu newspaper.

Kumar denies he was among those chanting anti-India slogans at last Tuesday's rally to mark the 2013 hanging of Kashmiri separatist Mohammed Afzal Guru over a deadly 2001 attack on the Indian parliament.

Protests against Guru's execution have regularly been held in Kashmir, where many believe he was not given a fair trial. Guru has always denied plotting the attack, which was carried out by Kashmiri militants.  

Police have also registered sedition cases against another five students who they say attended the rally, but have been unable to track them down.

On Tuesday around 100 right-wing activists staged a protest outside JNU, demanding that "traitors" be hanged.

The charge has been used in the past against supporters of independence for the disputed territory of Kashmir, which is divided between India and Pakistan and claimed in full by both.

Indian forces have since 1989 been fighting militant groups seeking independence for Kashmir or a merger with Pakistan.

Many Kashmiris associate more with Pakistan, a Muslim-majority Islamic republic, than with Hindu-majority India which is officially secular.