Australians from three tour groups are missing in the aftermath of Nepal’s devastating flash flooding, as the number of people accounted for climbed to 1500, with 162 dead.

Two young boys, aged 11 and 14, and a 64-year-old woman were in a group of 15 Australians on a two-week hike with Himalayan Glacier Adventures.

Another six Australians were with Kailash Journeys and one Australian was travelling with Kathmandu Holiday Tours and Travels.

The Australians were reportedly near the Himalayan border between Nepal and Tibet when sudden floodwaters triggered by a glacier landslide smashed the region on Wednesday morning local time.

At least 34 Australians are among 800 tourists unaccounted for.

Rescuers transport an elderly woman rescued from an old-age home following a flash flood in Trishuli Bazar, Nepal. Photo: AAP

One Australian tour group was hiking from Kathmandu to Mount Kailash but lost contact with the tour company after the landslide on Wednesday morning around 8.30am local time.

“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 US-based Himalayan Glacier team said in a statement.

Almost 1500 people are missing across Nepal and Tibet after a wall of ‌mud and rock collapsed into a Himalayan river, sending catastrophic floods through towns and valleys.

Rescuers in Nepal used helicopters to search for survivors and drop emergency supplies to thousands cut off in a rugged mountainous region thronged by ‌trekkers and pilgrims, linking Lhasa in Tibet with the Nepalese capital of Kathmandu.

Police said they expected the death toll to rise beyond 165.

“This will go up, as we have resumed the search and more bodies are expected to be recovered,” police spokesperson ‌Abi Narayan Kafle told Reuters.

Among the missing tourists from more than two dozen countries, 177 were from India, 63 were from the United States, 34 from Australia, 33 from Britain and 25 from Canada.

The tally of missing in Tibet’s Gyirong county was 558, Chinese state broadcaster CCTV said on Thursday, including 260 foreign nationals.

More than 5000 army and police rescue personnel were mobilised to look for survivors and find bodies.

Damaged houses in the aftermath on the Trishuli River in Nepal’s Nuwakot district. Photo: AAP

Pictures are now emerging of the shocking aftermath, with survivors being dragged out of thick heavy mud which blankets the towns in northern Nepal.

Vast expanses that were once built-up areas of towns are now nothing but an empty canvas of silt.

Foreign Minister Penny Wong confirmed DFAT was urgently working to locate the Australians, and crisis personnel would be deployed.

However, she said communications in Nepal was difficult.

Houses, roads and power projects were swept away in Nepal, while officials in Tibet said they feared “major casualties” after a mudslide hit a border land crossing in the county of Gyirong.

As darkness fell, authorities continued the grim task of recovering and ‌trying to identify bodies.

The debris-choked banks of the Trishuli River, Nepal. Photo: AAP

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.”

Albanese expressed his “deepest sympathies” to those affected by the flooding.

A suspension bridge in Nuwakot, Nepal. Photo: AAP

Wong said the loss of life and destruction caused by flash flooding was 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.

-with AAP