Eight million people have been affected by the massive earthquake in Nepal - more than a quarter of the country's population - the United Nations says.
International aid has started arriving but there is still huge need - 1.4 million require food aid, the UN said.
The 7.8-magnitude quake hit Nepal on Saturday destroying buildings in Kathmandu and severely affecting rural areas across the region.
The death toll has risen to 4,310, with almost 8,000 injured, officials say.
Nepal and surrounding areas have continued to experience aftershocks. Thousands in Kathmandu, Nepal's capital, spent a third night outside, too afraid to go back into their houses.
Water, food and electricity are in short supply and there are fears of outbreaks of disease.
"According to initial estimations and based on the latest earthquake intensity mapping, eight million people in 39 districts have been affected, of which over two million people live in the 11 severely affected districts," said the most recent report from the UN Office of the Resident Co-ordinator.
The situation is critical in the remote rural regions towards the epicentre of Saturday's quake.
"In the rural areas, 90% of the people have been affected by this calamity," Surya Mohan Adhikari, a district official in the remote town of Gorkha, told AP news agency. "They have lost their homes and livestock, they have no way of getting food."
"It is very difficult to reach them," he added. "They are cut off by landslides on the mountain roads, and the wind and rain is making it difficult for helicopters to land."
The Nepal government has pleaded for overseas aid - everything from blankets and helicopters to doctors and drivers.
"We urge foreign countries to give us special relief materials and medical teams. We are really desperate for more foreign expertise to pull through this crisis," said Chief Secretary Leela Mani Paudel.
Many countries have sent aid including India, China, the UK and US.
But there is a logjam at Kathmandu airport, with individuals trying to fly out of the country while flights of aid and rescue teams wait to land.
On Monday, four Indian air force aircraft had to return to Delhi international airport after encountering "congestion" at Kathmandu, tweeted a spokesman for India's defence ministry.
Hospitals are unable to cope with the huge numbers of people in need of medical attention and some Nepalis have complained of aid being slow to reach them.
The country's most deadly earthquake in 81 years triggered avalanches that have killed 18 people on Mount Everest - the worst disaster in history on the world's highest peak.
More than 200 people were trapped on the mountain but helicopters are bringing them to safety with about 60 rescued on Monday, according to the tourism ministry.
Expedition leader Chris Harling described experiencing the quake on the north side of Everest, telling the BBC the camp "started to vibrate underneath us which increased in intensity up to the point where the ground was literally shaking backwards and forwards like a giant jelly.