A woman claiming she hit a pedestrian wearing a clown suit and a man scaring teenage girls are among a spate of creepy clown reports police in Western Australia have recently received.

In one incident, a 19-year-old man allegedly chased a group of teenage girls while dressed as a clown in the main shopping district of Northam, east of Perth, on Saturday night.

Police said the scared teenagers were chased about 700 metres down Fitzgerald Street to the Northam police station on Gairdner Street.

"As officers opened the front door the man then ran from the scene but he was apprehended a short distance away," a police spokesman said in a statement.

The man was charged with disorderly behaviour and possession of a disguise.

In another incident, a woman reported she had hit a pedestrian dressed as a clown on Tonkin Highway in the Perth suburb of Champion Lakes.

The woman told police the pedestrian had gone into bushland nearby, but despite an extensive search involving the police air wing and dog section and paramedics, the person was unable to be found.

Several other incidents of people dressed as clowns were also reported to police overnight, but police were unable to find anyone wearing clown disguises.

"It is important to remember that dressing as a clown isn't against the law, however should a person engage in activity that is criminal, anti-social or threatening towards other people, police will investigate," the spokesman said.

He said possessing a disguise was illegal if it was used to conceal identity while committing an offence.