A Massey University academic is getting online bashing for his work on right-wing Hindu nationalist groups.

Dean's Chair in Communication Professor Mohan Dutta says Hindutva trolls have been flooding his social media accounts in recent weeks, some of them abusive and calling on Massey University to fire him and retract his work.

"I get that with white supremacists," said Dutta, who also addresses hate and white supremacy in his work, "but the sheer scale of this is really the first time."

He is getting up to 80 Twitter and Facebook messages and tags a day calling him names like "grade A twat", "stinking a**hole" and "boot licker".

"And not just from one or two, but a set of different people and what seem like organisations," he said.

Dutta's work critiques Hindutva ideology and maps the influence of Islamophobia in Indian groups associated with it.

Hindutva seeks to establish the hegemony of Hindus and Hinduism in a secular India, a movement that has gained ground since Narendra Modi's nationalist Bharatiya Janata Party came to power in 2014. Critics describe the ideology as extremist right-wing, even fascist.

"Hinduism is not Hindutva," says Dutta, who is Hindu and believes the trolls' attempt to silence criticism is an attack on academic freedom in universities across the globe, including in New Zealand.

A Massey University spokesperson says the professor became a target of Hindutva activists after he gave an online talk on August 24, ahead of an international conference the university is co-sponsoring along with some 70 other institutions called "Dismantling Global Hindutva".

Organisers and speakers of the online conference kicking off tomorrow (10-12 September) have also been harassed by Hindutva activists trying to stop the event from going ahead, according to Al Jazeera.

It is not clear who is behind the trolling, how many there are and where they are located.

"It's this world of digital hate you can't really track," Dutta says.

They are different individual Twitter accounts, including some that seem like organisations with websites.

"These organisations that supposedly speak for Hindu human rights, but when you actually dig into the organisation it says its goal is to prevent the conversion of Hindus into Christianity and Islam," he said.

At least one Twitter account with the handle NamasteKiaOra seemed to be based in New Zealand and had posted comments shortly after the LynnMall terror attack, but the account has since been taken down.

Dutta is doing "critical mahi" exposing Hindutva in Aotearoa and being targeted for it, says Dr Sapna Samant of the Aotearoa Alliance of Progressive Indians (AAPI), a collective of activists, artists, academics and physicians.

"It is a well-developed intimidation strategy," says Samant, who has also been a target of name-calling on Twitter, and threats on email and over the phone.

She says Hindutva reduces India into a Hindu nation where all other religious minorities, especially Muslims, are outsiders.

More than 100 international academics, activists and civil society groups have signed a letter of support for Dutta and his Massey University research centre CARE.

"It is vitally important, both for Massey University as well as the civic world in general that CARE's academic freedom be defended strongly when it is attacked," said the letter.

"We reject the idea that critiquing Hindutva is in any way harmful to Hindu students and Hindu communities. Hindutva is the most significant threat to Hinduism's pluralist ethos, as well as to efforts to fight casteism and sexual violence targeting women."