India’s police say they have arrested a 20-year-old man they suspect created an online app that shared pictures of Muslim women for a virtual "auction”, as an investigation into the case of religious hatred widens.

An open-source app on the Microsoft-owned Github platform called "Bulli Bai” – a derogatory term to describe Muslim women – had shared pictures of dozens of women without their consent before it was taken down a week ago.

K P S Malhotra, a police official in the capital, New Delhi, on Thursday said his team had arrested Niraj Bishnoi, a 20-year-old engineering student, from Jorhat in the northeastern state of Assam after a probe that involved the state-run Computer Emergency Response Team.

"He is the person who had created the Bulli Bai app on Github. He had also created the Twitter handle @bullibai_ and other handles,” Malhotra said.

Police in the western city of Mumbai, who are also investigating the app, have separately arrested three people this week, including two 21-year-old engineering students – Vishal Kumar and Mayank Rawal – and Shweta Singh, a 19-year-old woman.

Mumbai police said they were investigating whether the app, which did not involve any actual auctioning of people, was part of a "larger conspiracy”.

‘Absolutely chilling’

Several Indian Muslim journalists were targeted by the app, including Ismat Ara who filed and then shared on social media a police complaint on Sunday that said the app was "designed to insult Muslim women”.

"After today’s arrest by @DelhiPolice, I hope the culprits behind this elaborate harassment of Muslim women, including journalists like myself, will ultimately be caught & punished,” Ara said in a tweet on Thursday.

Media watchdog Reporters Without Borders (RSF) described the app as "absolutely chilling” and urged Indian authorities to take action.

"To do nothing would be to condone an extremely violent form of harassment, a form of intimidation that discriminates against an entire sector of the journalistic community and exposes those targeted to potential physical attacks,” RSF’s Daniel Bastard said.

Singh, the youngest of those arrested so far in the ‘Bulli Bai’ app case, is from the northern Indian state of Uttarakhand.

The 19-year-old began spending time on social media and made contact with Hindu right-wing users after finishing her school-leaving exams last year, a local police official who spoke to her earlier this week told Reuters news agency.

The official, who declined to be named, said Singh had told him that her actions were based on Hindu right-wing ideology, which she had picked up on social media platforms, including Facebook, WhatsApp and Twitter.

"She came to social media to distract herself but she kept getting entangled in it,” the official said.

Muslims, who account for about 14 percent of India’s 1.3 billion population, have witnessed a rise in religious hatred and violence since Prime Minister Narendra Modi came to power in 2014 and was re-elected with a bigger majority in 2019.

In July last year, a similar app, named ‘Sulli Deals’, also on GitHub, had put nearly 80 Muslim women "for sale”. No arrests have yet been made in that case.

Many women who appeared on both the apps have in the past made critical statements on the rise of Hindu nationalism and the treatment of minorities in India.