A dangerous fire flared up in southeastern Australia on Sunday even as cooler conditions elsewhere allowed authorities to begin assessing the damage from blazes that swept through two states on Saturday.

Officials told residents and others in the New South Wales (NSW) state town of Eden to leave immediately and head north if they did not have a bush-fire response plan.

"If your plan is to leave, or you are not prepared, leave towards Merimbula or Pambula," the Rural Fire Service said in an alert.