A 23-year-old man is clinging to life in intensive care after he was bashed at Midland Oval last night.
It is believed he was struck with a piece of wood.
A police spokeswoman said a 23-year-old man, 29-year-old man and 31-year-old man were "assisting with inquiries".
She said officers arrived at the oval on Keane Street just before 7.30pm to find the 23-year-old with serious head injuries.
St John Ambulance paramedics took the man to Swan Districts Hospital where he was assessed and transferred to Royal Perth Hospital.
An RPH spokesman said he remained in the intensive care unit this morning.
Midland detectives are at the scene this morning.Anyone with information is asked to call Crime Stoppers on 1800 333 000.