Two men were injured during a "serious disturbance" on the streets of St Andrews in the early hours of Saturday.
Police Scotland received reports of 8-10 youths fighting in the Abbey Street area of the Fife town at about 02:40.
Two men were taken to Ninewells Hospital in Dundee with serious but non-life threatening injuries.
Officers believe the trouble was linked to the theft of a motorbike, and resulted in youths chasing each other and throwing bottles.
Det Ch Insp John Anderson said: "This was a serious disturbance which has left two young men with serious facial injuries.
"The group involved are described as being in the 18/23 years old age band, and were wearing jeans and jumpers. We believe they were in the St.Andrews town centre for some time last night under the influence of alcohol and people may have cause to have been alarmed about their behaviour.
"From our enquires, we understand that a group of males have been involved in a physical confrontation that started on Playfair Terrace culminating on Abbey Street when these males were injured.
"We know that during this time, the males confronted and chased each other by throwing bottles on Bell Street and South Street and believe that people in the town that night would have seen this."
Officers want to speak to anyone who witnessed the trouble, especially taxi drivers parked at the rank on Bell Street who may have dashcam footage of the incident.
Det Ch Insp Anderson added: "We also believe this incident to be linked to the theft of a motorbike from an address on the Canongate that was reported shortly after 3am. This motorbike is possibly now in the Methil area.
"We are carrying out door to door enquiries and reviewing CCTV images in the area as part of the investigation."