New bushfire threatens WA homes

A watch and act alert has been issued with lives and homes under threat from an "out-of-control and unpredictable" bushfire in Perth's south.

Firefighters battle a bushfire near Cockburn, south of Perth, Feb 3 2014 (AAP).

Lives and homes are under threat from an "out-of-control and unpredictable" bushfire in Perth's south.

A watch and act alert has been issued for people in Mandogalup in the City of Kwinana.

Residents have been warned to leave or get ready to actively defend their properties.

The fire started between Anketell Road and Mandogalup Road at 1.40pm (WST) on Wednesday and is burning north towards Anketell Road.

The cause of the fire is unknown.