A woman has suffered red welts after an unknown liquid was thrown over her by a teen on a busy bridge in Perth’s south at the weekend.

Police are hunting a male who approached the victim, who is aged in her 30s, as she stood on the pedestrian walkway under the Mount Henry Bridge in Applecross on Saturday afternoon.

“The liquid came into contact with the woman’s right arm and right leg, and caused an immediate burning sensation,” a WA Police spokesperson said.

“Upon arriving home, the woman noticed the liquid caused her to have red welts where it had struck her.”

Police said the attack happened near the southern end of the 660m-long bridge between 5.10pm and 5.20pm, and the teen had approached on an e-scooter.

The offender was with two other youths also riding e-scooters, and he was last seen near Curruthers Rd.

The incident was reported to police on Tuesday, triggering an investigation.

Anyone with information should contact Crime Stoppers.