A teenager had her nose broken after being attacked by three girls.
The 14-year-old girl, who was with a friend of the same age at the time, was also treated for deafness to one ear following the assault in Wolseley Road, Coldean, on July 19.
The two victims were attacked at around 5.30pm.
Detective Constable Duncan Lloyd described the incident as “nasty” and “violent”
He said: "We would like to speak to any witnesses and especially to a woman who interrupted the incident.”
A 13-year-old and 14-year-old girl, both from Brighton, were arrested on suspicion of assault. They were questioned and released on bail until August 24.
A 15-year-old girl, also from Brighton, was arrested on suspicion of assault. She has been questioned and released on bail until August 26.
Anyone who witnessed the incident should contact police on email@example.com or call 101 quoting serial 1868 of 19/07. Alternatively, call the Crimestoppers anonymously on 0800 555 111.