In a shocking incident of 'moral policing', a couple travelling on the Kolkata Metro was allegedly thrashed by their co-passengers for “being too close”.

The incident, reported in a section of the media with purported pictures of the assault, sparked protests outside the metro station on Tuesday.

According to the media reports, a man hugging his female friend raised eyebrows in a train compartment on Monday night. A few people objected to it, following which an argument ensued between the two sides.

The mob then allegedly heckled the couple, pushed them out of the train and beat them up, the reports said.

Condemning the incident, citizens, carrying placards, gathered outside the Dumdum metro station on Tuesday, demanding a suo motu case by the Railway Police Force (RPF) against the assaulters.

Indrani Banerjee, the spokesperson of the Metro Rail, said appropriate action would be taken in the matter if the victims came forward with a complaint.

The Metro Rail does not support moral policing of any kind, she added.

"We have asked the station master, the RPF personnel on duty (about the incident), but none of them could confirm what happened. There is also no official complaint by any passenger. We are eager to conduct an inquiry if we get a lead," Banerjee said.

Photographs of the alleged assault have gone viral on the social media, sparking an outrage by authors, artists and the common people.

"Is my city dying...I am tormented beyond words by yesterday's incident in the metro rail...I apologise on behalf of the children of my city," music composer Debojyoti Mishra wrote on Facebook.

The post was accompanied by a sketch of a couple in an embrace.

Author Taslima Nasreen also expressed her indignation over the incident.

"A young couple embraced in Kolkata metro. It made a bunch of frustrated old losers angry. They beat them up. Scenes of hatred are allowed. Scenes of love are considered obscene," she wrote on Twitter.