American scouts were preparing to pull out too as South Korea grapples with one of its hottest summers in years.
Hundreds of participants have been treated for heat-related ailments since the Jamboree began on Wednesday in the coastal town of Buan.
A group of more than 900 Australian scouts aged between 14 and 18 are among the event's 45,000 participants.
The World Organisation of the Scout Movement has asked South Korean organisers to "consider alternative options to end the event earlier than scheduled and support the participants until they depart for their home countries".
Should organisers decide to proceed, there needs to be stronger assurances "they will do everything possible to address the issues caused by the heat wave by adding additional resources", the body said in a statement.
"We continue to call on the host and the Korean government to honour their commitments to mobilise additional financial and human resources, and to make the health and safety of the participants their top priority," it said.
The statement came after the UK Scout Association announced it was pulling out more than 4000 British scouts from the jamboree and moving them into hotels.
The departure of the jamboree's largest national contingent represented a huge public relations setback for the South Korean hosts, who scrambled to continue the event.
Hundreds of American scouts were also expected to depart the site on Sunday and relocate to a US military base near the South Korean capital, Seoul, said an email the contingent sent to members.
It said leaving was necessary because of the "extreme weather and resulting conditions".
The US Embassy in Seoul did not immediately respond to questions on whether the plan to accommodate the scouts at Camp Humphreys had been finalised.
But the South Korean organising committee confirmed the Americans were among three national contingents that decided to leave as of Saturday afternoon, a group that also included dozens of Singaporean scouts.
Organisers have cancelled activities requiring hard physical effort and added more emergency vehicles, medical staff and air conditioning to the site, while Seoul's Foreign Ministry is operating a special task force to address concerns raised by foreign diplomatic offices over the safety of the event.
South Korean President Yoon Suk Yeol promised an "unlimited supply" of air-conditioned buses and refrigerator trucks to provide chilled water to the site.
South Korea this week raised its hot weather warning to the highest level for the first time in four years, and temperatures around the country hovered between 35 and 38 degrees Celsius on Friday.
According to South Korea's Ministry of the Interior and Safety, at least 19 people have died from heat-related illnesses across the country since May 20.
The jamboree scouts from 158 countries to a campsite built on land reclaimed from the sea.
Long before the start of the event, critics raised concerns about bringing that many young people to a vast, treeless area lacking protection from the summer heat.
According to South Korea's government, 138 Jamboree participants received treatment for heat-related illnesses on Thursday alone.
At least 108 participants were treated for similar ailments following Wednesday's opening ceremony.
Choi Chang-haeng, secretary-general of the jamboree's organising committee, insisted the event was safe enough to continue.
He linked the large number of patients Wednesday to a K-pop performance during the opening ceremony, which he said left many of the teens "exhausted after actively releasing their energy".
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