A rare species of marsupial, the eastern quoll, has been born in the wild on the Australian mainland for the first time in more than 50 years.

The native animals were once found along Australia's east coast until they were devastated by foxes and disease.

Scientists in New South Wales (NSW) reintroduced the species from Tasmania earlier this year and now three females are carrying joeys in their pouches.

The bean-sized babies will stay growing inside the pouches for three months.

Nick Dexter, who works for the Booderee National Park where the species was reintroduced, said the development marked an important step.

"There remains challenges ahead to establish a sustainable population, but to have thirty percent of the female quolls produce pouch young from this pilot project is a move in the right direction," he told AFP news agency.

"We've been tracking every animal in this project with a GPS collar and... we've been able to quickly discover and manage threats."

The eastern quoll is a furry carnivore that grows to be the size of a domestic cat. It mainly eats insects, and was spotted regularly on Australia's mainland up until the 1960s.

In March, about 20 were released into the park and they have been closely monitored by conservationists using movement-sensitive cameras.

Australian National University researcher Natasha Robinson said the animals had shown the potential to succeed in the long-term.

"We've proven that quolls can find food, shelter and breed. We've also shown a capacity to make changes to improve the quolls survival rate," she told AFP.