Police incident shuts down Mitchell Freeway Powis Street off-ramp as man in 50s fights for life

A man is fighting for life and a Mitchell Freeway exit has been shut by police after an early-morning incident.

Drivers are being re-routed at Powis Street in the northbound lane of the freeway by traffic incident response and multiple police vehicles.

Exact details of the incident, understood to be an assault, are still unfolding.

St John Ambulance took a man in his 50s from nearby Dodd Street to hospital with severe injuries after an incident about 2.22am.

He was raced to Royal Perth Hospital under lights and sirens, arriving about 3.20am.

Main Roads alerted the closure of the Powis Street off-ramp about 4am. Police have been on the scene since.

Detectives were seen working at a scene, with disposable gloves on the ground at a second location at the Gallup Powis Street carpark.

Two detectives were seen in discussion with a police officer, pointing towards the road.

Police in high-vis trench coats used small torches while walking carefully across the grass next to the off ramp, also combing through the bordering hedges.

Two more police vehicles arrived at the scene shortly before 7am.