Bushfire threatens southern Perth suburbs

A bushfire is burning out-of-control in Perth's southern suburbs, shutting a major freeway.

Kwinana Freeway has been shut in both directions from Mortimer Road and Mundijong Road due to smoke from a fast-moving fire in Baldivis.

Firefighters are treating the bushfire as suspicious and police are now looking for the arsonist on a day that reached 31.7 degrees in Perth and some outer suburbs as high as 35.

A watch and act is in place for people in northern Baldivis, with an unpredictable blaze nearing people in the area of Kwinana Freeway to the east, Bertram Road, Wellard Road and Millar Road.

Emergency services are warning residents to leave or get ready to defend their properties as the fires could threaten lives and homes.

The fire started near Millar Road.

Meanwhile, an alert has been downgraded to advice level for people in Australind, bounded by Collie and Brunswick Rivers, north to Paris Road and west to Barnes Avenue.

Firefighters have controlled but not contained a fire which started at about 1.30pm.

Firefighters are on the scene at both blazes.