A man was left needing stitches to his face following an attack in Sincil Bank in Lincoln.
The incident happened at around 6pm on Friday, April 25, when a man approached a group of three young men to ask if one lying on the ground needed any help.
There was an altercation between the group and the man was then attacked with a weapon, thought to have been a knife.
Police say the victim sustained a cut to his face and underneath his jaw, for which he was taken to hospital and required six stitches.
Detectives said the attack was unprovoked and are appealing for information to help trace the offenders, who are described as three young white men.
One is thought to have been aged around 13-15, about 5ft 3in in height, with mousey brown short hair, and of skinny build. He was wearing a grey or blue hooded top.
The other two are described as aged around 12 and smaller in height. One may have been speaking Polish.
Anyone with any information relating to the attack or who was in the area of Sincil Bank, the football ground and surrounding area, and who heard or saw anything suspicious is asked to contact Lincolnshire Police on 101 quoting incident number 347 of April 25.