The appeal by West Midlands Police focusses on attacks by two girls at a McDonald's on Stephenson Place in Birmingham and on Smallbrook Queensway at around midnight on December 15 and 16 last year.
The girls are suspected of attacking a cleaner at the McDonald's restaurant, as well as a man who came to her aid. They were then said to have attacked two women on Smallbrook Queensway, pulling them to the floor by their hair, punching one in the face and stamping on another while she was on the ground.
The force has launched an appeal for information with locating the girls.
A spokesman for West Midlands Police said: "Do you recognise these two girls? We need to speak to them over a series of unprovoked assaults in Birmingham city centre.
"It’s understood they attacked a cleaner in McDonald's, Stephenson Place at around midnight on 15-16 December, plus a man who came to the woman’s aid.
"We believe they went on to attack two women in Smallbrook Queensway, pulling them to the floor by their hair, punching one in the face and stamping on another while she was on the ground.
"Three teenagers were involved in the assaults. We’ve already identified and arrested one suspect, aged 17, but we’re asking for your help to find these two.
"These were nasty, unprovoked assaults on people enjoying a night out and we need to trace them.
"If you think you recognise them please get in touch. You can speak to Crimestoppers anonymously on 0800 555111 or message us on Live Chat through our website. Or you can call us on 101.
"Please quote crime ref 20/1929411/21. Thanks."