Sam the koala, who gained worldwide fame and sympathy when she was rescued during Australia's devastating wildfires, died today during an operation to save her from a life-threatening disease.

The four-year-old koala had developed cysts associated with urogenital chlamydiosis, which affects up to 50 per cent of Australia's koala population.

During surgery, the disease was found to be so advanced that it was inoperable and Sam was put to sleep, said spokeswoman Peita Elkhorne.

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"It was so severe that there was no possible way to be able to manage her pain.

"All of those who have been involved with Sam are devastated with this loss."

Even Australian prime minister Kevin Rudd commented on the animal's death, saying she had been a symbol of hope for Australia during the wildfires.

"It's tragic that Sam the koala is no longer with us," Mr Rudd said.

As the fires burned in Victoria state, Sam was making her way on scorched paws past a fire patrol north of Melbourne when one of the firefighters spotted her.

The firefighter was photographed holding a bottle of water to her lips, an image that was seen around the world.

She suffered second and third-degree burns to her paws and had been recuperating at the Southern Ash Wildlife Shelter.

Record temperatures, high winds and forests dried by years of drought set off infernos that swept a vast area of Victoria state, killing more than 170 people and destroying thousands of homes.