KATHMANDU (AFP) - Nepalis started fleeing their devastated capital on Monday after an earthquake killed more than 3,800 people and toppled entire streets, as the United Nations prepared a "massive" aid operation.
With fears rising of food and water shortages, people were also rushing to stores and petrol stations to stock up on supplies in the capital, ripped apart by Saturday's 7.8-magnitude quake.
And fears were rising of disease outbreaks among tens of thousands of traumatised survivors who have been camping out in parks and other open spaces in Kathmandu.
"Right now, it is important to prevent another disaster by taking precautions against an outbreak of diseases among the survivors," army spokesman Arun Neupane told reporters.
Families were packing onto buses, some even sitting on the roofs, and into cars, to leave the city for their home villages to determine the extent of the damage there.
Mothers clutching their children and men hauling bags were seen bargaining with drivers of the many buses clogging the roads out of the capital.
The exodus came as international rescue teams with sniffer dogs raced to find survivors buried in rubble, and teams equipped with heavy cutting gear and relief supplies landed at the nation's only international airport.
Officials say more than 3,800 people are now known to have died, including 3,793 in Nepal - making it the quake-prone Himalayan nation's deadliest disaster in more than 80 years.
More than 90 people have been killed in neighbouring India and China while a further 6,509 people were injured in Nepal.
Elisabeth Byrs, a spokeswoman for the UN's World Food Programme, told AFP the agency would launch a "large, massive operation" with the first plane carrying rations set to arrive on Tuesday.
Thousands of Nepalis have lost their houses, forcing them to set up tents in parks, while others are too terrified to return home after several powerful aftershocks.
"This is a nightmare. Why don't these aftershocks stop?" asked 70-year-old Sanu Ranjitkar, clutching her dog and with an oxygen mask strapped to her face as she sat under a tarpaulin.
With just plastic sheets to protect them from the elements, many were desperate for aid and information on what to do next.
"There is just too much fear and confusion," said Bijay Sreshth, who fled to a park with his three children, wife and mother when the quake hit.
Long queues formed outside petrol stations while supermarkets were seeing a run on staples such as rice and cooking oil.
A government official said tonnes of clean water and other essential supplies were needed for survivors as well as stepped-up search and rescue efforts outside the capital.
"We need more helicopters for our rescue operations in rural areas," home ministry spokesman Laxmi Prasad Dhakal told AFP.
"We also need supplies of essential goods such as food and clean water to provide relief for survivors."
- Rescue on Everest -
The quake triggered an avalanche on Mount Everest which buried part of base camp in a cascade of snow and rock, killing at least 18 people Saturday on the world's highest mountain.
Rescue helicopters on Monday airlifted climbers from higher altitudes on the mountain where they were stranded above crevasses and icefalls, after evacuating scores of seriously injured from base camp the day before.
Hundreds of mountaineers had gathered at Everest at the start of the annual climbing season, and the real scale of the disaster there has been impossible to evaluate with communications all but cut off.
- 'Why do we suffer?' -
Reconstruction efforts in impoverished Nepal could cost more than $5 billion, or around 20 percent of the country's GDP, according to Rajiv Biswas, Asia Pacific chief economist at business research firm IHS.
Much of the historic centre of Kathmandu is in ruins and the chaos has been worsened by power cuts while the cellphone network is at breaking point.
Nearly a million children living in affected areas are in urgent need of humanitarian assistance, UNICEF said.
Nepal's army said crews trying to rescue those trapped in the rubble of high-rise buildings were being hampered by a lack of proper equipment.
"We need more equipment that can detect sounds and help track survivors," said Colonel Naresh Subba.
In Kathmandu's Balaju neighbourhood, one father endured the agony of watching police pull the body of his daughter from the rubble of their home after using a combination of a mechanical digger, hammers and bare hands.
"She was my everything. She didn't do anything wrong, she didn't have to die," said Dayaram Mohat as he collapsed in grief on hearing the news of his 14-year-old daughter Prasamsah's death.
- Food and blankets -
The Nepalese rescuers were being joined by hundreds of foreign aid workers from countries including China, India and the United States.
Around 70 US aid workers, along with rescue dogs, headed to Nepal aboard a military transport plane which flew from Delaware.
The European Commission released 3.0 million euros (S$4.34 million) in emergency aid which will help fund clean water, medicine, emergency shelter and telecommunications.
Hospitals have been overwhelmed, with morgues overflowing and medics working flat out to cope with an endless stream of victims suffering trauma or multiple fractures.
The quake's epicentre was around 73km east of the town of Pokhara, the country's centre for adventure sports. An AFP correspondent reported the town had been largely unaffected and tourists were continuing their holidays.
Nepal and the rest of the Himalayas, where the Indian and Eurasia tectonic plates collide, are particularly prone to earthquakes.
A 6.8 magnitude quake hit eastern Nepal in August 1988 killing 721 people, and a magnitude 8.1 quake killed 10,700 people in Nepal and India in 1934.