Detectives have released CCTV images after a pregnant woman was assaulted at Waterloo Underground Station.
The incident happened at 7.30am on Sunday 24 May.
The victim, a 34-year-old woman, was on board a Northern line train and asked a man, who was also travelling on the same train with a group of people, to move his feet so could sit down.
The man moved his feet and then became abusive and put his feet up on her lap and started kicking her.
Other members of the group also joined in by verbally abusing the woman and as the train stopped at Waterloo the group assaulted her again. The group then ran towards the Jubilee line where they boarded a train.
DC Oliver Carne said: "This was an appalling attack on a pregnant woman and her unborn child.
"The woman is in the early stages of pregnancy, but thankfully the baby was unharmed, I am extremely keen to speak to the people in the CCTV images as they may have witnessed what happened on the day.
"Any information will prove invaluable to this investigation so please get in touch by calling or texting us on the number below."
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference T-SUB/B12 of 19/06/15. Information can also be passed anonymously to independent charity Crimestoppers on 0800 555 111.