While he was reporting from protests on Swanston Street about 11.15am on September 21, a man in high-visibility gear grabbed Seven News journalist Paul Dowsley by the neck in a headlock.

A second man, with a bald head and wearing a brown jacket, spat on Mr Dowsley before a third man in a bicycle helmet threw urine at the journalist.

At 12.30pm, a fourth man threw a drink can at Mr Dowsley, which hit him in the head, police said. He was wearing a beanie and blue clothing.

Victoria Police said the behaviour was "unacceptable" and have released photos of four men they want to speak to.

Many of the incidents were filmed by camera crews and police are asking for witnesses to come forward.

Last month's protests started with construction workers storming their union building over mandatory vaccination rules, but turned into wider unrest across Melbourne over several days.

Australian Associated Press