US-based travel company Himalayan Glacier Adventures confirmed 15 Australians, including the two boys aged 11 and 14, were on a tour when floods swept through the region, with fears growing for their safety.
Founder and chief executive Sagar Pandey told AAP the group lost contact after the landslide on Wednesday about 8.30am local time.
Nine males and six females are among the Australians missing with the group.
"The flooding has been severe and has caused significant disruption in the affected area," the Himalayan Glacier team said in a statement.
"Unfortunately, due to damage to mobile networks and electricity infrastructure, communication remains extremely difficult, and we have not yet been able to establish contact with anyone there."
The federal government is urgently working to locate Australians who went missing along the Himalayan border between Nepal and China, where a huge wall of mud and rock collapsed into a river on Wednesday.
Nepali police said late on Wednesday that 157 bodies had been recovered so far.
Prime Minister Anthony Albanese urged Australians in the affected area to follow the advice of local authorities.
"We are aware of a number of Australians in the area and Australian officials are urgently working to confirm their welfare," he said in a statement.
"We are liaising with local authorities as well as tour operators. We stand ready to provide consular assistance."
Mr Albanese expressed his "deepest sympathies" to those affected by the flooding.
Shyam Rana lives in Melbourne and spent the night speaking with family members in Nepal who are thankfully safe away from the immediate destruction.
Scenes in Nepal have been described as chaotic, with communication difficult.
"I've heard it's hard to get any rescue emergency vehicles into the area because of the land," he told AAP.
"It's hard to land helicopters and it's hard to get the cars trucks and army vehicles into there."
He's yet to speak with extended family near the impacted region.
Opposition Leader Angus Taylor backed in the call to follow local advice.
"Our thoughts are with all those affected by the devastating flooding in Nepal and Tibet, including the families who have lost loved ones and those still waiting for news," he said.
The loss of life and and destruction caused by flash flooding is devastating, Foreign Minister Penny Wong said.
"Our thoughts are with the loved ones of those killed or missing and all affected by this disaster," she said in a statement on Thursday morning.
Australian Ambassador to Nepal Simon Ernst released a statement together with the embassies of the United Kingdom, France, Finland, Norway and Switzerland.
"Our thoughts are with all those affected by this disaster. We express our solidarity with the people of Nepal during this difficult time," they said.
Australians in need of urgent help should contact the Department of Foreign Affairs and Trade's 24- hour consular emergency centre.
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