Eight million people have been affected by the weekend earthquake in Nepal that killed nearly 4,400 people and 1.4 million people are in need of food assistance, the United Nations has said.
UN resident co-ordinator in Kathmandu, Jamie McGoldrick, said that of those affected two million people are in the 11 worst-hit districts.
He said that 72 hours after Saturday's magnitude-7.8 quake, "people are still in a very much hard-ship mode". The challenge of supplying to small villages at high altitudes and in rough terrain "is quite significant", he said.
After flying by helicopter over Dhulikhel town, on the north side of the Kathmandu valley, Mr McGoldrick estimated that about 40% of the houses were damaged, but the destruction was erratic. "Some areas on one ridge are completely untouched, on the other side it's completely flattened," he said.
Helicopters today crisscrossed the skies above the high mountains of Nepal's Gorkha district near the earthquake's epicentre, ferrying the injured to clinics, and taking emergency supplies back to remote villages.
Two helicopters brought in eight women from Ranachour village , two of them clutching babies to their breast, and a third heavily pregnant.
"There are many more injured people in my village," said Sangita Shrestha, who was pregnant. She was quickly surrounded by Nepalese soldiers and policemen and ushered into a waiting van to be taken to a hospital.
The little town of Gorkha, the district's administrative and trading centre, is being used as a staging post to get rescuers and supplies to those remote communities. Some villages were reachable only by air after landslides blocked mountain roads.
Some women who came off the helicopters were grimacing and crying in pain and unable to walk or speak, in agony three days after being injured in the quake.
Sita Karki winced when soldiers lifted her. Her broken and swollen legs had been tied together with crude wisps of hay twisted into a makeshift splint. "When the earthquake hit, a wall fell on me and knocked me down. My legs are broken," she said.
After an hour of dark clouds gathering and threatening rain, the wind kicked up in Gorkha and sheets of rain began to pour down. Geoff Pinnock, of the UN's World Food Programme, was leading a convoy of trucks north toward the worst affected areas when the rain began to pound, leaving them stuck.
"This rain has caused a landslide that has blocked my trucks. I can maybe get one truck through and take a risk driving on the dirt, but I think we'll have to hold the materials back to try to get them out tomorrow by helicopter," he said.
Aid workers who had reached the edges of the epicentre described entire villages reduced to rubble.
"In some villages, about 90% of the houses have collapsed. They're just flattened," said Rebecca McAteer, an American physician who rushed to the quake zone from the distant Nepal hospital where she works.
And yet, the timing of the earthquake - near midday, when most rural people are working in the fields - meant most villagers were spared of injuries when buildings collapsed, she said. So far, police say they have 373 confirmed deaths in the Gorkha district.
Most those injured, she added, were young people and the elderly, since most young men long ago left their villages in search of better-paying work.
"The immediate need is getting support to where it's needed, but there will be a lot of work rebuilding," said Ms McAteer, who was heading back soon to the centre of the quake zone.
Thomas Meyer, an engineer with the International Nepal Fellowship who accompanied Ms McAteer to the devastated villages, noted the disaster's aftermath would stretch long into the future.
"This is a long-term emergency," he said. "This will need major attention for the next five years. People have nothing left."
Across central Nepal, including in Kathmandu, the capital, hundreds of thousands of people are still living in the open without clean water or sanitation. It rained heavily in the city yesterday, forcing people to find shelter wherever they could.
At Kathmandu airport, flights arrived with emergency aid and helicopters brought in both foreign trekkers and local Nepalese villagers from quake-struck areas. Nepal's economy relies heavily on tourism and trekking, including near Mount Everest, the world's tallest.
Helicopters chartered by trekking companies reached the Langtang area, about 40 miles (60km) north of Kathmandu, a popular trekking area.
The United Nations is releasing 15 million US dollars (£9.8 million) from its central emergency response fund for quake victims. The funds will allow international humanitarian groups to scale up operations and provide shelter, water, medical supplies and logistical services, UN spokesman Farhan Haq said.
Trucks carrying food were on their way to affected districts outside the hard-hit and densely-populated Kathmandu valley, and distribution of the food was expected to start today.
Citing government figures, Mr Haq said an estimated 8 million people have been affected by the quake in 39 of Nepal's districts, and more than 1.4 million need food assistance, including 750,000 who live near the epicenter in poor quality housing.
The UN humanitarian country team for Nepal is co-ordinating international relief efforts with the government and a clearer picture of needs should emerge within the next 48 hours, he said. The immediate priority is search and rescue, and removing debris to find survivors still trapped, he said.
Buildings in parts of the capital, Kathmandu, were reduced to rubble, and there were shortages of food, fuel, electricity and shelter. As bodies were recovered, relatives cremated the dead along the Bagmati River, and at least a dozen pyres burned late into the night.
Many of the ornate, historic buildings in Bhaktapur, a key tourist site just east of Kathmandu, were reduced to rubble. Residents began returning to collect whatever belongings they could.
The country's death toll has risen to 4,355, said Deputy Inspector General of Police Komal Singh Bam. Another 61 were killed in neighbouring India, and China's official Xinhua News Agency reported 25 dead in Tibet. At least 18 of the dead were killed at Mount Everest as the quake unleashed an avalanche that buried part of the base camp packed with foreign climbers preparing for summit attempts.
Some 8,063 people have been injured, Mr Bam said. Tens of thousands are believed to be homeless.
Rescue workers and medical teams from at least a dozen countries were helping police and army troops in Kathmandu and surrounding areas, said Major General Binod Basnyat, a Nepal army spokesman. Contributions came from large countries like India and China - but also from Nepal's tiny Himalayan neighbour of Bhutan, which dispatched a medical team.
Medical and rescue teams from Russia, Japan, France, Switzerland and Singapore were expected in Kathmandu over the coming days, the Nepal army said.
Fearful of strong aftershocks, tens of thousands of families spent a third night outdoors in parks, open squares and a golf course, bundled against the chilly Himalayan night.