Three people waiting at a bus stop in Churchill Square, Brighton, were pepper-sprayed in the face by a man in a passing car.
All three victims, two men aged 20 and one aged 21, instantly felt their eyes and faces burning.
They were given medical treatment at the Royal Sussex County Hospital in Brighton.
It is not known exactly what substance was sprayed in their faces.
Sussex Police said today that the incident happened on Thursday 9 June at about 2.40am as the three victims were waiting at a bus stop.
They were in Churchill Square in Western Road, Brighton, after a night out in the city centre.
A red Peugeot, possibly a 106, drove along Western Road with the passenger hanging out of the window shouting and gesturing at people on the pavement.
The car, a left-hand drive model with a French number plate, then flashed its lights at those at the bus stop.
The passenger got out of the car and became aggressive.
The driver went to the boot and, after initially approaching the group holding a large dark canister with a black handle and yellow nozzle, returned to the car with the passenger.
As they drove off the passenger leant out of the window and sprayed the canister in the faces of the three victims.
The car then drove off towards North Street.
The two men are described as Arabic and aged about 25 years old.
The driver was slim, about 5ft 8in tall and with short dark shaven hair.
The passenger was described as lanky and 6ft tall with short dark curly hair.
A police spokesman said: “The victims were shaken by the ordeal.
“I am appealing for anyone who witnessed the incident or has any information about a red hatchback with a foreign licence plate to contact police on 0845 6070999.”