About 30 bikers from Scotland's Blue Angels Motorcycle Club rode along the roads of Aberdeenshire at the weekend.
A police spokeswoman said: "Police Scotland are making enquiries into two incidents of assault which occurred in the early evening of Saturday.
"One was in the King Street area of Aberdeen and the other was in the Foveran area of Aberdeenshire.
"Police Scotland have carried out investigations into these incidents during Saturday and Sunday and inquiries have centred on a number of motorcyclists who appear to have been visiting the north-east."
The first incident took place in a BP petrol station in King Street around 6pm on Saturday night.
The second took place in the Foveran area just off the A90 Aberdeen to Ellon road.
Police Scotland said four men from the Aberdeen area, aged 47, 50, 51, and 53, were due to appear in court yesterday in connection with the two alleged assaults.