Specialised rescue teams from China, India and Nepal built temporary bridges to reach remote areas and dug through the ruins of hydropower projects, using excavators to try to rescue nearly 300 workers trapped inside tunnels.
A glacier collapse on August 26 sent a deluge of ice, rock and mud sweeping through the impoverished country's border region with China.
The death toll rose to 1050 while about 4000 people remain missing, including 583 foreigners of which 42 are Australians.
At least 639 people remain stranded in devastated hydropower stations that have become the focus of rescue efforts, Nepal's disaster management authority said on Tuesday.
The disaster left at least 2.2 million tonnes of debris, according to a preliminary estimate by the United Nations Development Program (UNDP), including parts of buildings, rocks and sediment.
"The amount of debris shows the scale of the destruction and the challenge communities face as they clear homes, roads and public spaces and begin to rebuild," it said.
More than 11,000 people have been rescued and power and communication lines were restored in some areas, Prime Minister Balendra Shah said in a social media post.
"We did not have the time to grab anything before fleeing," said a survivor from the hard-hit Rasuwa district, who had walked to Nuwakot with scores of other survivors.
"What we were wearing is the only pair of clothes we have. And even they are wet from rain."
In China, rescue teams worked through the night to reopen access to the Nepali border, on a steep mountain gorge flanked by unstable cliffs and fast-flowing river channels.
China will send DNA testing experts to disaster-hit areas and a second batch of relief supplies, including drones and water purification, its foreign ministry said.
South Korea, nine of whose citizens were working at a hydropower project and are missing, said it will send a 44-member emergency relief team to support search-and-rescue operations in Rasuwa.
Nepal last week declined foreign participation in general search and rescue but said it needed specialised services and advanced technological support in areas such as life-detecting machines, large refrigerators and pre-fabricated bridges.
Aid worth more than $US42 million ($A59 million) flowed into the country after the disaster, Shah said, with contributions expected to increase.
Shah said 279 workers were rescued from hydropower projects, with joint teams from Nepal, India and China working on search-and-rescue operations.
Rescuers are contending with collapsed tunnels and floodwaters that have made access difficult at several hydropower sites where the largest numbers of people are believed trapped, an army source said.
"Our first rescue observation at Trishuli Hydro Power plant shows that it is not humanly possible to go into the tunnel," Asish Gurung, a mountain guide helping in the tunnel rescue, told Reuters from Haku village in Rasuwa district.
"We need machines like bulldozers and excavators ... There may be about 500 people trapped inside," he said.
There has been a boom in hydropower projects in Nepal since the turn of the century as the mountainous country sought to take advantage of its Himalayan water resources to address chronic domestic power shortages and expand electricity exports to neighbouring India.
Shah said the disaster signalled the growing risks the Himalayan region faces from a warming planet.
"The time has come for us to strongly raise before the international community the disasters we are experiencing as a consequence of climate change," he said.
