The World Health Organisation (WHO) has announced circulating vaccine-derived poliovirus type 2 has been detected in stool specimens of two healthy children in PNG earlier in May.
It is the first outbreak of the debilitating virus in PNG since 2018, with the WHO testing centred on the city of Lae, in New Guinea's north.
Wastewater samples have also picked up the highly-infectious virus - particularly in regions with poor sanitation - in the capital of Port Moresby.
Australia's Pacific Minister Pat Conroy said his government would fund vaccines through WHO with the potential to reach three million children.
"Vaccination is the most effective way to prevent the spread of polio," he said.
"That's why we are working closely with the government of Papua New Guinea to step up vaccination efforts to protect children and ensure a healthy region."
PNG vaccination rates are estimated at around 44 per cent, given rise to the potential for outbreaks.
Polio, which is often carried without symptoms, primarily affects children, with a small number of cases causing paralysis and even death.
Rates of the virus have plummeted in recent decades owing to a global eradication program, with polio now endemic in only Pakistan and Afghanistan.
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