Four people were sprayed by a white liquid in a series of linked attacks across Tayside on Monday evening.
Police are appealing for information about the incidents in Coupar Angus and Dundee.
The first attack took place at approximately 9.30pm in Causewayend, Coupar Angus, when a father and his child were sprayed with a white liquid by the occupants of a white Audi that drove past them.
Then, at around 10pm on Dundee’s Blackness Road, a 17-year-old woman was sprayed with liquid by the occupants of what police believe to be the same car as it drove past her.
Finally, at about 10.10pm outside the Marco Polo takeaway in Hawkhill, Dundee, another young woman was sprayed with liquid by the occupants of the white Audi.
Police Scotland said in a statement: “Fortunately no one was injured in any of these incidents, and the liquids sprayed on the victims have not been harmful, however they did not know this immediately at the time and were left alarmed and upset.
“This behaviour is not only extremely childish but potentially very dangerous, and not funny in the slightest.
“We are following a positive line of enquiry, however, we would still like to hear from anyone who has information about any of these incidents, or anyone who may have been targeted as there may have been more instances which we have not been informed of.”
The car involved is described as a white Audi, possibly an RS4 or similar.
The driver has been described as a heavily built man, and the liquids were sprayed from the passenger side by one or two other males.
Anyone with information is asked to call 101 or speak with any police officer.
Information can be given anonymously through CrimeStoppers on 0800 555 111, quoting incident reference 3919 of 25th May.