In pictures: Australia fires the size of Manhattan

At least half of Australia's only disease-free koala population, a key "insurance" for the species' future, is feared dead with more badly hurt after bushfires swept through an island sanctuary, rescuers said Sunday. Kangaroo Island, a popular nature-based tourist attraction off the coast of South Australia state, is home to many wild populations of native animals including the much-loved koala, where the populated was estimated at 50,000. Massive bushfires have flared up in the vast country's southeast in a months-long crisis, killing nearly half a billion native animals in New South Wales state alone, scientists estimate.

Conditions have been particularly severe in recent days, with an ongoing blaze on Kangaroo Island spreading rapidly and razing 170,000 hectares - one-third of the island - on Friday. "Over 50 percent (of the population) has been lost," Sam Mitchell of Kangaroo Island Wildlife Park, which is raising funds to care for the injured koalas, told AFP. "Injuries are extreme. Others have been left with no habitat to go back to, so starvation will be an issue in coming weeks."

A University of Adelaide study published in July found that the Kangaroo Island koala species is particularly important to the survival of the wider population as it is the only large group free from chlamydia. The bacterial infection - which causes blindness, infertility and death in the species - is widespread in koalas in the eastern Queensland and New South Wales states and also occurs in Victoria state. "They are an insurance population for the whole population," the University of Adelaide's Jessica Fabijan, who carried out the study, told AFP. "These fires have ravaged the population." Fabijan said massive bushfires in New South Wales and Victoria's Gippsland region, home to major koala populations, is also expected to have killed many animals. "It's one of the biggest tragedies for the population since the late 1800s when they used to hunt them for their fur," she added.

This image made from video shows dead kangaroos and sheep after wildfires hit the Kangaroo Island, South Australia Sunday. In the state of New South Wales alone, almost 150 fires continued to burn, many out of control, with light rains offering little relief and blazes again touching the suburbs of Sydney. Everywhere, people struggled to come to grips with a catastrophe that has taken place on a near-continental scale, unfurled over months and altered daily life for millions.

- Authorities are assessing mass property damage across southeastern Australia after searing temperatures and strong winds exacerbated catastrophic wildfires Saturday in one of the worst days of the weeks-long crisis. Milder weather, including patchy rain, across southeastern Australia has brought some relief, though firefighters continue to battle two "emergency-level" blazes in New South Wales and four in Victoria, hampered by flame-fanning wind gusts, authorities said Sunday. Dozens of communities, from small towns on the south coast of New South Wales, to alpine villages in neighboring Victoria state, faced extreme conditions as fires grew so large they generated dry thunderstorms.

Thousands of people, including tourists, had heeded the advice of authorities and evacuated a 350-kilometer stretch of coastline as well as dangerous inland areas over the past few days to escape the intensifying infernos. But many remained, hosing down their properties to protect against falling embers as they anxiously waited to see if the winds would blow the fire front in their direction.

Stunned Australians on Sunday counted the cost from a day of catastrophic bushfires that caused "extensive damage" across swathes of the country and took the death toll from the long-running crisis to 24. Hundreds of properties were destroyed and one man died trying to save a friend's home in the severe conditions - among the worst in Australia's deadly bushfire crisis. But even as Australians tried to regroup, seaside towns were plunged into darkness, ash rained down on rural communities and major cities were again cloaked in smoke on Sunday.

On Saturday, Prime Minister Scott Morrison announced the largest military call-up in living memory, mobilising up to 3,000 reservists to assist exhausted volunteer firefighters. Warships and combat helicopters have already been repurposed to help out with the largest maritime evacuation in Australia since World War II - moving some of the 4,000 people trapped for days on the foreshore of Mallacoota to safety. Up the coast, thousands of people remained displaced and many more are weighing an uncertain future. Queen Elizabeth II on Sunday said she was "deeply saddened" by the fires, and thanked the emergency services "who put their own lives in danger" to help communities.

Celebrities have pledged or raised millions of dollars to support firefighters and fire-affected communities, including American pop star Pink, who tweeted on Saturday that she was donating US$500,000. Australian actress Nicole Kidman matched that pledge. "Our family's support, thoughts and prayers are with everyone affected by the fires all over Australia," she posted on Instagram. "We are donating $500,000 to the Rural Fire Services who are all doing and giving so much right now."