Bushfire emergency for WA's South West

An out-of-control bushfire is threatening lives and homes in Western Australia's already fire-ravaged South West region.

An emergency alert has been issued for the John Tognela Rest Area on the Forrest Highway, in the Shire of Waroona, after the fire was reported after 11am on Friday.

The Department of Fire and Emergency Services advises residents to leave the area immediately if the way is clear.

An evacuation centre has been set up at the Waroona Recreation Centre, while aerial support has been sent to help crews fighting the fast-moving blaze.

A watch and act warning has also been issued for people east of Harvey River, south of Kooljerrenup Nature Reserve, Hills Road and Mounsey Road, north of Dorrsett Road and Old Bunbury Road, and west of Gibbings Road.

Waroona Police have tweeted that the bushfire is suspicious.