More than 6,500 were injured and thousands are living in tents after their homes were destroyed.
Dozens of people are also reported to have been killed in neighbouring China and India.
At least 200 climbers have now been rescued around Mount Everest, after the quake triggered avalanches.
Vast tent cities have sprung up in Nepal's capital, Kathmandu, for those displaced or afraid to return to their homes. Thousands spent Sunday night - their second night - outside.
There are shortages of water, food and electricity, while disease is also a concern.
"We urge foreign countries to give us special relief materials and medical teams," Nepal's government Chief Secretary Leela Mani Paudel said.
China and India have sent emergency teams, along with Pakistan, which said it was dispatching four C130 transport planes carrying a 30-bed hospital. Other countries, including Britain, Australia and New Zealand are also contributing.
However, congestion at Kathamandu's airport has caused delays, with Indian TV reporting that an Indian relief flight was forced to turn back.
United Nations World Food Programme spokeswoman Elisabeth Byrs told AFP that the agency planned "a large, massive operation".
Officials have warned that the number of casualties could rise as rescue teams reach remote mountainous areas of western Nepal.
Many communities, especially those close to mountainsides, are believed to have suffered significant quake damage.
"Villages like this are routinely affected by landslides, and it's not uncommon for entire villages of 200, 300, up to 1,000 people to be completely buried by rock falls," said Matt Darvas, spokesman for aid agency World Vision.
A man evacuated by helicopter to Pokhara, 200km from Kathmandu, said almost every home in his village of more than 1,000 houses had been destroyed, Mr Darvas told the BBC.
In Dhading district, 80km west of Kathmandu, people were camped in the open, the hospital was overflowing, the power was off and shops were closed, Reuters news agency reported.
A senior official in Gorkha district, the location of the earthquake's epicentre, told AP he had heard reports of 70% of houses being destroyed.
Among villages affected are some inhabited by Tibetans, many of whom have sought refuge in Nepal. Bridim, north of Kathmandu, is reported to have been virtually flattened.
Rescuers are continuing to recover bodies from under the rubble of collapsed buildings in Kathmandu.