A group of violent thugs left a London Underground passenger with a fractured skull and cheekbone after a row on a platform.
The argument allegedly concerned a woman "singing and dancing" on a train, police said.
Officers added the victim was punched in the face before being repeatedly kicked after he collapsed and lay unconscious on the ground.
Detectives issued CCTV images of the suspects and are appealing for witnesses to come forward.
The incident happened at Barbican tube station in central London just after midnight on July 12.
Police said the victim and a group of people began arguing about a female "singing and dancing" on-board the train.
A British Transport Police spokeswoman said: "As the victim got off the train, a man from the group charged at him and punched him repeatedly in the head causing him to fall to the floor and lose consciousness.
"The rest of the group then kicked him as he lay on the floor.
"As a result of the attack the victim suffered a fractured skull, fractured cheekbone and had multiple teeth knocked out.
"Officers believe the people in the image may have information which could help their investigation."
Anyone with any information is asked to contact BTP by texting 61016 or calling 0800 40 50 40.
Yesterday, footage emerged of a violent brawl at West Ham tube station in east London.
A clip shared on Twitter showed a woman, dressed in a red and white striped top, black trousers, and a leather jacket, shouting at a second woman, who was wearing a light pink dress and floral headpiece.
After squaring up to each other, the woman dressed in red accused the second woman of spitting on her.
The second woman then turned and walked away, as a third woman – who was on the phone – tried to calm the pair down by standing in between them.
At this point, the second woman turned back around and restarted the confrontation – but things quickly turned nasty.
Within seconds, the two women began hitting and slapping each other in front of dozens of other commuters who watched on.
