Officials at Nepal's tourism ministry told media outlets that around 340 foreigners were among more than 400 tourists missing after the disaster, which hit a mountainous region popular with trekkers and pilgrims.
Among the missing were 47 from the United States, 34 from Australia, 33 from the United Kingdom and 24 from Canada, said Sunil Sharma, a tourism board spokesman.
Houses, roads and power projects were swept away in Nepal, while officials in Tibet said they feared "major casualties" after a mudslide hit a border land crossing in the county of Gyirong.
"It was a huge gush of mud coming straight towards us. As it got closer, it kept rising higher and higher. When I saw it enter our home, I tried to grab my wife's hand and take her to the terrace. But she was swept away by the mud," said Keshav Prasad Baral, a 68-year-old survivor, who was being treated at a small hospital.
"Four or five hours later, a helicopter came to rescue me. My wife is still somewhere beneath the mud. She's gone."
Another survivor described being saved by clinging to a mango tree as he watched the house where he had been working disappear.
Initial reports from Nepali officials suggested an earthquake in the area could have caused the lower part of a glacier to collapse and trigger the floods.
Security footage captured on the Chinese side of the Nepal-Tibet border showed many people fleeing before a torrent of rock, mud and water destroyed buildings, vehicles and took many lives.
As darkness fell, authorities continued the grim task of recovering and trying to identify bodies.
At least 62 missing Nepali citizens were among hundreds of locals trekking in the Gosaikunda Lake area in Rasuwa, coinciding with the local festival of Janai Purnima on Friday, Sharma added.
Nepal police spokesman Abi Narayan Kafle told the Associated Press at least 28 police officials were missing.
Local media reported 65 people were being treated in hospitals in the area and in the capital Kathmandu.
South Korea separately said nine of its citizens working on a hydropower plant were missing.
China's state broadcaster said three people were killed and 265 missing in Gyirong.
It said the toll was still being verified and rescue efforts were ongoing.
With the deluge of muddy water sweeping down from an estimated nearly 2000 metres above sea level, flood alerts were issued in the populous northern Indian states of Uttar Pradesh and Bihar, which border Nepal and where several rivers flow down the mountains into the plains.
Authorities in Bihar said they had relocated about 5000 people from six districts and planned to move a total of 10,000 to 12,000 people.
Security footage captured on the Chinese side of the Nepal-Tibet border showed many people fleeing before a torrent of rock, mud and water destroyed buildings and vehicles and took many lives.
The German Research Centre for Geosciences said there was a 4.4-magnitude quake approximately seven minutes before the time shown on the security footage time-stamp.
Television images showed collapsed homes, floating cars and a metal bridge being washed away, while witnesses told Reuters the waters engulfed entire villages.
"There could be heavy casualties or loss of property," said district administrator Narendra Pariyar, who urged dwellers on the banks of the Bhote Koshi river - into which the Lhende Khola empties - to move to higher ground.
From its origins in Tibet, the Bhote Koshi river empties into Nepal's Trishuli river, which eventually flows into India as the Gandak river.
with AP
