Australian authorities issued new warnings and evacuation notices across the country's heavily populated southeast on Thursday as a return of hot weather fanned huge bush fires threatening several towns and communities.

A disaster notice in Victoria state, already in place for the past week, was extended by two days and people in danger zones were told to leave. In neighboring New South Wales state, authorities told residents to prepare for worsening weather conditions on Friday.

"These fires are absolutely still moving, still growing in our landscape and they pose significant risk to communities," Victoria Emergency Services Minister Lisa Neville said in a televised briefing.