Policeman hurt in knife scuffle with woman

A Perth policeman has suffered an knife-inflicted injury in a struggle with a seemingly unhinged woman.

Concerned members of the public called police after seeing the woman behaving erratically on a Morley street at about 10.45pm (WST) on Wednesday.

When a 22-year-old police officer checked on her welfare, she pulled out a knife and they struggled.

The officer received a puncture wound to his chest during the scuffle.

The injury was not life-threatening, WA Police said, and he was treated at Royal Perth Hospital.

The 20-year-old woman is under medical assessment and investigations into the incident are underway.