Police Scotland officers in Dumfries are carrying out enquiries into the serious disturbance which took place at about 5.40 pm on Saturday.
At that time, a large number of youths were seen to be involved in the disturbance, and early indications are that assaults were taking place.
On police intervention, three men were found to have been assaulted.
A 21-year-old man was found with bruising to his face and a cut to his back and two men aged 20 and 19 had received minor injuries.
DC Paul Steele of Police Scotland said: “The town was very busy around this time with the Guid Nychburris celebrations in full swing.
“We want to hear from anyone who may have witnessed what was a serious disturbance on the Mill Green at this time involving up to eight to ten youths, all of who appeared to be in their mid teens and were wearing causal sports type clothing.
“Anyone with any information can contact police at Dumfries on the 101 number.”