WELLINGTON (AFP) - Thousands of people have signed a petition for koalas to be introduced to New Zealand to escape Australia's devastating bush fires, but the proposal has been given the thumbs down by officials.

A group calling itself the Koala Relocation Society said koalas were "functionally extinct in Australia" but could thrive in New Zealand which has nearly 30,000ha planted in eucalypts, which are koalas' preferred food and shelter.

There have been estimates of up to a billion koalas and other animals affected by the fires raging across Australia, and haunting images of koalas with singed fur, possums with burnt paws and countless charred kangaroo carcasses have flashed around the world.

One third of Kangaroo Island, a wildlife haven off the coast of South Australia state, has been razed and there are fears some species unique to the area might have been wiped out.

There are also concerns about how the surviving animals will cope, given the loss of vegetation.

As of midday on Monday (Jan 13), the online petition had 7,500 signatures, but a spokesman for Prime Minister Jacinda Ardern told Television New Zealand that the government's focus was on helping to get the fires under control so koalas "can stay in their natural habitat".

Wellington Zoo animal science manager Simon Eyre believed any assistance should be provided directly to the Australian authorities dealing with the fallout from the fires.

"For us, it would be assisting in Australia and it wouldn't only be koalas, it would be other species affected by the fires as well," he said.