Emergency warnings in place for Perth bushfire

Homes have been saved in Perth's east as authorities work to battle a megablaze threatening communities.

Residents in Red Hill, Millendon, Herne Hill and Baskerville in the City of Swan, about 20km from the CBD, have been told they are in danger and need to act to survive.

The fire started near Toodyay Road in Gidgegannup about 12.30pm on Tuesday.

So far some 650 hectares have been burned as the West Australian Department of Fire and Emergency Services tries to manage the blaze.

DFES incident controller Murray McBride said authorities were working around Aboriginal cultural sites in the firezone.

"We've got Indigenous liaisons working with us at the moment to identify those sites and that will dictate where we can put those machines," he said.

Windy conditions and steep country have been hampering DFES efforts to battle the blaze, though conditions are set to improve later in the week.

"With the fire activity going down hopefully we can get some people back into their homes," Mr McBride said.

Containment lines will be put in place on Wednesday evening, allowing for easier access for firefighting crews.

As of Wednesday afternoon a dozen houses were under threat, though DFES were confident they would be saved.

Earlier on Wednesday, Acting Superintendent Paul Postma said air support was be needed to battle the blaze.

"They'll be doing a lot of retardant drops through the bush area, trying to contain the fire and preparing for the extreme winds that we have got forecast today," he said.

"We don't have any reports of homes lost but we do have reports of damage to two sheds and a number of (fences) and minor property damage."

Mr Postma said he still had concerns about the fire around the rural properties as conditions worsened on Wednesday.

Some 120 firefighters, including volunteers, are involved.

The department said residents must leave if the way is clear, or prepare to shelter at home.