A second powerful earthquake in less than three weeks spread panic in Nepal on Tuesday, bringing down buildings weakened by the first disaster and killing at least 66 people, including 17 in India and one in Chinese Tibet.
Most of the reported fatalities were in villages and towns east of Kathmandu, only just beginning to pick up the pieces from the April 25 quake that left more than 8,000 dead.
The US military's Pacific Command said a Marine Corps helicopter involved in disaster relief had gone missing, with six US Marines and two Nepalese soldiers aboard.
The new 7.3 magnitude quake was centred 76 km (47 miles) east of the capital in a hilly area close to the border with Tibet, according to coordinates provided by the US Geological Survey, and unleashed landslides in Himalayan valleys near Mount Everest.
Villagers who watched their homes collapse said they only survived because they were already living in tents.
Aid workers reported serious damage to some villages in the worst-affected Charikot area and said some people were still trapped under rubble. Witnesses said rocks and mud came crashing down remote hillsides lined with roads and small hamlets.
"We still don't have a clear view of the scale of the problem," said Dan Sermand, emergency coordinator at medical NGO Medecins Sans Frontieres, which surveyed the area by air and saw multiple landslides.
The United Nations has only raised 13 per cent of the $423 million it said was needed to help Nepal recover from the April quake, which measured 7.8. Relief workers said they were already suffering a lack of material before the new quake.
"Why are (internally displaced people) sleeping on our office floor? Where are our tents? Where are our tarpaulins? Where are our hygiene kits?" said Brian Kelly of the International Organisation for Migration, at a large relief camp in the hill-top town of Chautara, hard-hit by both quakes.
"They need to be paid for," he said.
A team of about a dozen volunteers searched the rubble for survivors in the town, the biggest in a district that suffered the worst casualties in April. Several people were believed to be trapped. "It's better to search at night so it's quiet," said Rejoien Guru, a volunteer from Kathmandu.
He and others pointed flashlights into the decimated buildings hit by the twin quakes, calling out for survivors. "If anyone is in there, make a sound!" he called in Nepali.
FAMILY WATCHES HOUSE DISAPPEAR
In the town of Sangachowk, residents were outside receiving government food aid when the new quake struck. A family sat on the edge of the road where their house had just fallen down the hill, rubble spread over hundreds of feet below.
"We watched it go down slowly, slowly," said Ashok Parajuli, aged 30.
In Charikot, where at least 20 bodies were recovered, hotel owner Top Thapa said the quake was at least as strong as last month.
"We saw houses falling, collapsing along the ridge," said Thapa, owner of Charikot Panorama Resort. He said he saw five or six multi-storey buildings come down.
Politicians dashed for the exit of Nepal's parliament building in Kathmandu, and office towers swayed as far away as New Delhi. The tremors that began at around 12.30 could be felt in Bangladesh and were followed by a series of powerful aftershocks.
Parents clutched children tightly, and hundreds of people frantically tried to call relatives on mobile phones. Shopkeepers closed their stores and the streets were jammed with people rushing to check on families.