PNG's National Disaster Centre said more than 2000 people had been buried alive by Friday's landslide in remote Enga province.
The Albanese government will send technical experts and $2.5 million in initial aid as the death toll continues to rise.
Pacific Minister Pat Conroy described the situation as "incredibly grim" and sent his condolences to the nation.
"I'm advised access can only be achieved through helicopters, so the search and recovery efforts are very, very, challenging," he told ABC News Breakfast on Tuesday.
"We stand ready to support Papua New Guinea in any way they need it.
"We're the closest neighbours and the dearest of friends, and we owe them a debt of gratitude for their assistance in our floods our bush fires ... and we'll do anything they need to support them in this disaster."
Mr Conroy said the support provided by Australia was only an initial commitment and more would flow at the request of PNG's government.
He said the true extent of the disaster wasn't yet known.
"This is an incredibly inaccessible part of Papua New Guinea and it's a really challenging process for everyone involved," Mr Conroy said.
Under the Australian aid package experts will provide incident management assistance, support geo-hazard assessments and help early recovery efforts, with the Australian Defence Force also assisting.
Villagers have spent days searching through rubble. (AP PHOTO)
Treacherous terrain in the region and difficulty getting in aid has hampered rescue efforts, raising fears few survivors will be found.
The head of the International Organisation for Migration in PNG Serhan Aktoprak said the conditions on the ground were hampering rescue and aid efforts.
Rocks were still falling from the mountain, soil was cracking and water was flowing under the debris.
All Australians will be thinking of Papua New Guinea at this very difficult time.— Richard Marles (@RichardMarlesMP) The Australian Government will provide an initial $2.5 million in humanitarian assistance to support PNG's response to the landslide in Enga Province.May 27, 2024
"We're just hoping that in the remaining short window of time we have, we can at least contribute to the relief efforts in saving some more lives," Mr Aktoprak said.
"But unfortunately, (time) is not on our side."
A spokesperson for United Nations Secretary-General Antonio Guterres said he was "deeply saddened" by the reported loss of hundreds of lives.
"He extends his heartfelt condolences to the families of the victims and expresses his solidarity with the people and government of Papua New Guinea," the spokesperson said.
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