Live updates: Thousands flee homes as fires spread; Major heatwave to hit millions; Properties feared lost in blazes

Fire crews across Victoria are battling multiple blazes burning at an emergency level as extreme winds and high temperatures create "catastrophic" conditions.

Two major fires at Longwood and Walwa continue to burn out of control with multiple properties confirmed destroyed.

Three people - two adults and a child - also remain unaccounted for.

Across the border, NSW is in the grips of an extreme heatwave with health authorities warning people to avoid the health risks that come with it.