Hardcore pornography that flashed onto a giant screen at one of Delhi's busiest metro stations has prompted red-faced rail authorities to launch an investigation, an official said Sunday, after footage of the incident was shared widely online.

Commuters were stopped in their tracks at the station in the Indian capital's central business district of Connaught Place last weekend when the x-rated footage began playing on a large screen that normally broadcasts advertisements for luxury property or credit card schemes.

Scores of people captured the moment on their mobile phones and the images have since gone viral on social media.

Delhi Metro Rail Corporation (DMRC) spokesman Mohinder Yadav told AFP Sunday that authorities were trying to identify three suspects believed to be behind the incident last Sunday.

DMRC said the offending screen was operated by a private company and had an unsecure WiFi network, leaving it accessible to others.

“As per CCTV footage, three men have run (the) porn clip through their mobile on this TV,” the DMRC said in a statement late Saturday, adding that the contractor in charge of the screen would be required to have password protection from now on.

The incident made headlines in a country where talk about sex or even public displays of affection are seen by many as taboo.

Mainstream cinema is stripped of raunchiness by India's socially-conservative censor board, which muted the word “lesbian” from a Hindi-language film, blocked the release of a toned-down version of the erotic movie “Fifty Shades of Grey” in 2015, and deemed two James Bond kissing scenes unsuitable for an Indian audience. (NEW DELHI AFP)