PNG Police revised the death toll in the country's highlands to 26 after revealing they'd received the "wrong head count".
Police believe the men were shot dead in an ambush in the Enga Province, in a major escalation of tribal fighting in the region.
Prime Minister Anthony Albanese said the Australian government was ready to assist its Pacific neighbour.
"That is very disturbing the news that has come out of Papua New Guinea," Mr Albanese said on Monday.
"We remain available to provide whatever support we can in a practical way, of course, to help our friends in PNG."
The violence was connected to a battle between two tributes, local media reported.
Security remains a major issue in PNG, with at least 16 people killed in January riots sparked by economic uncertainty and unrest.
The violence broke out as Foreign Minister Penny Wong and Pacific Minister Pat Conroy announced the government was boosting support for PNG with a package aimed at addressing major health challenges including HIV and malaria.
The funding was drawn from the government's $620 million Partnerships for a Healthy Region initiative, which will help build up health systems in the Pacific and Southeast Asia.
Senator Wong said Australia would continue to work with its neighbour to meet health challenges.
"We cannot have the peaceful, stable and prosperous region we want without improving the health and wellbeing of our region's communities," she said.
PNG leader James Marape visited Australia in early February, addressing a joint sitting of the federal parliament and meeting with the prime minister.
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