Investigations have been launched after hardcore porn was screened on a giant screen at one of Delhi's busiest metro stations.

Embarrassed officials confirmed that they have started a probe after footage of the incident, which took place on 9 April, went viral online line.

According to AFP, commuters at the Indian capital's central business district of Connaught Place were astonished when the X-rated footage started playing on a large screen in the metro station.

The screen normally features advertisements for luxury property or credit card promotions.

Travellers managed to capture the video on their mobile devices and posted it on social media.

Delhi Metro Rail Corporation spokesman Mohinder Yadav said three suspects were believed to be behind the incident.

The company said that the screen was operated by a private company which had an insecure WiFi network.

"As per CCTV footage, three men [ran the] porn clip through their mobile on this TV," the rail company said.

It added that the contractor responsible for screenings would in future be required to have password protection to prevent a repeat of the incident.