Officials from Australia are working urgently to confirm the welfare of those reported missing after catastrophic flooding and a landslide hit communities near Nepal's border with Tibet, Foreign Minister Penny Wong said on Friday.
More than 390 people have died and hundreds more remain unaccounted for, including 39 Australians, up from 34 announced on Thursday morning.
Senator Wong confirmed the additional four missing Australians had been travelling separately to tour groups.
Additional personnel to support Australians affected by the disaster will be sent to the region, she said.
"The extraordinary scale of this disaster and the remoteness of the affected region mean immense challenges lie ahead for the response and recovery," a statement from her office read.
The government will provide humanitarian support including food, emergency shelter and medical support and has established a $5 million assistance package for affected communities.
An initial team of three humanitarian response specialists will be sent to help 20 staff already on the ground in Nepal.
"Our thoughts are with the loved ones of those affected as we urgently work to confirm the welfare of missing Australians," Prime Minister Anthony Albanese said in a post to social media.
The missing include 15 Australians who were on a trek with US travel company Himalayan Glacier Adventures.
Sydney doctor Manoj Dharmaratnam, who was invited to join the 15 on the sacred pilgrimage but chose not to go, prescribed several of his close friends with altitude medication and conducted injury assessments before they left Australia.
"One of them had an injury and I did tell her, maybe you're not fit to go on this trek," Dr Dharmaratnam told AAP.
"She actually called up and cancelled her trip...but then she said I've bought the ticket, so I might as well go."
Included in the Himalayan Glacier group was a well respected Sydney couple with two sons in their 20s who were both studying medicine in NSW.
"They're such pioneers in the community of ours. They're very well known and well respected, so it's such a shame," Dr Dharmaratnam said.
The last contact with the family came at 8.30 local time, when one of the sons informed his girlfriend they were checking out of their hotel in Nepal's Langtang Valley.
"We just want to know something...that's all we're trying to do, you know, we just want to known they're safe," Dr. Dharmaratnam said.
"Miracles do happen and we've heard miracles are happening, so fingers crossed we are hoping they'll be fine."
The region was "extraordinarily remote and very difficult to traverse", complicating rescue efforts, former Australian ambassador to Nepal Felicity Volk told ABC Radio National on Friday.
"The terrain is so difficult to traverse that it will make, as we're seeing, this rescue effort almost impossible without roads, without communications," Ms Volk, who is director of the Australian Himalaya Foundation, said.
"That will also make it very difficult for the Australian government to access any information about the missing Australians."
Senator Wong said DFAT is assisting with 43 consular cases related to the matter.
"We are urgently working to identify how many Australians have been in the region and to confirm the welfare of any Australians who are not accounted for," she told ABC Radio.
She said the number of missing Australians could rise.
Nepalese-Australian families gathered for prayers and held a minute's silence for those lost to the floods on Thursday night.
Smartraveller has updated its travel advice, urging people to exercise a high degree of caution because of major flash flooding and a mudslide.
Australians in need of urgent help should contact DFAT's 24-hour consular emergency centre.
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