Four students detained over viral gang-rape video on WhatsApp

Four pupils from an Indian high school have been detained after a clip showing them gang-raping a younger student was seen by the victim's aunt after being circulated on WhatsApp, police said Friday.

The traumatised 15-year-old had kept quiet about the assault at the beginning of the month in Mumbai after being threatened with reprisals by her attackers who then uploaded the clip on the video messaging service.

But she gave a full account of what happened after her aunt saw the video and then went to see her niece at her home earlier this week.

"The aunt rushed to the girl's home after seeing the clip on WhatsApp and the girl broke out of her shell to narrate the whole story. They then registered the complaint and we acted," Dhananjay Kulkarni, a deputy commissioner with the Mumbai police, told AFP.

All those detained are aged 16 to 17 years-old.

"They have confessed and are now in Dongri," Kulkarni added in reference to a juvenile detention facility in India's teeming commercial capital.

There has been fierce debate in recent days over how India should treat minors accused of sexual offences ahead of the imminent release of a teenager convicted of an infamous gang-rape on board a bus in New Delhi.

Four adults who were also convicted of the fatal attack in 2012 have been sentenced to death, but the youngest of the gang is expected to go free in a matter of weeks after serving less than three years in detention.