A man was left with a broken hand after being kicked to the floor in an Aylesbury High Street attack.
The 19-year-old victim was walking down the road with friends shortly before 3.10am on Sunday when they were approached by five or six men.
One of the men then assaulted the victim.
The attacker is believed to be in his late teens, but a description has not been issued.
Anyone with information should contact Det Con Stephanie Macleod by calling 101 or call Crimestoppers anonymously on 0800 555 111.