A man has died fighting a wildfire that razed wooded hills near Australia's west coast city of Perth, destroying at least 27 houses.

Flames prevented paramedics from reaching the man who collapsed on the roof of his home in suburban Hovea on Perth's eastern fringe on Sunday. The ambulance service said he died at the scene while attempting to protect his house.

It was not immediately clear if the house was destroyed.

The state fire service said in a statement on Monday that 27 homes had been confirmed destroyed, adding that "this number is expected to increase as damage assessments continue."

The service said two firefighters were treated for heat exhaustion on Sunday.

About 150 firefighters on Monday continued to fight the blaze.