Videos showed people fleeing uphill in terror to escape the surging muddy flood waters.
Rescuers are searching for dozens of British nationals who are among those missing and feared dead in Nepal after devastating flash floods killed more than 150 people.
Nepal Police said on Wednesday evening that 157 bodies had been recovered following flooding in the Rasuwa region of Nepal, which borders China’s autonomous region of Tibet.
The Nepal Tourist Board said on Wednesday that the number of missing people had risen from 384 to 403, with 33 UK citizens among 341 foreign nationals unaccounted for.
Flash floods caused rivers to swell their banks and spread thick mud across populated areas, burying houses and creating difficult conditions for rescuers.
Videos posted on social media showed huge flood waters surging through valleys as people screamed in terror, with bridges being washed away.
Other videos showed people desperately fleeing uphill to escape the surging muddy flood waters.
The United States Geological Survey (USGS) said a magnitude 5.2 seismic event occurred near the border between Nepal and China on Wednesday at 8.37am local time.
It added that a “glacial collapse and debris flow” caused “subsequent catastrophic impacts downstream”.
Kalpana Malla, from Nepal’s Nuwakot district, told BBC News: “My family members were swept away by the flood in front of my eyes.”
Ms Malla said her father, mother, sister and her sister’s children were all swept away by the floods.
She added: “They could not escape the flood, there was no chance at all.
“This flood took everything, but my son and I climbed the rooftop of a house and survived, but couldn’t explain how.”
Rajan Shrestha, the mayor of Bidur municipality, told The Times that he had “never seen such a massive flood in my life” and estimated that about 400 people may have been swept away.
He added: “And it came so fast. We could not evacuate all the people from the main town.”
Sunil Sharma, a tourism board spokesman, said 133 of those missing were from India on pilgrimage to Mount Kailash in Tibet – a sacred site for Hindus.
Also among the missing were 47 people from the US, 34 from Australia, and 24 from Canada, he added.
According to the tourist board, 203 of the missing are male and 200 female.
Tour operator Alpine Eco Trek said a 13-year-old girl was among the missing British nationals, as well as two Irish citizens.
Among the missing British nationals are three men aged 65, 64, and 52, and seven women aged 44, 47, 51, 60, 63, 63, and 65, according to travel logs obtained by the Press Association.
The firm, which offers guided tours and expeditions in Nepal, confirmed four of its Nepalese tour guides – aged 38, 35, 45 and 29 – are missing as well.
Kumar Adhikari, the manager of Alpine Eco Trek, told the Press Association: “I feel so sad. We are just thinking about what to do next.
“We are in pain at the moment, deep pain.”
Mr Adhikari said the tour group, who were on a nine-day tour to Mount Kailash, were crossing into Tibet from Nepal when they became trapped at the border as the flash floods struck.
He said he was in contact with his tour guides until 8.40am when their phones went offline, at which point the group would have been inside Tibet’s immigration office.
“We were hoping that inside it was safe,” he said. “But later the video came from China’s government which (showed) even Tibet’s side was hit by the flood.”
In its analysis, the USGS said: “This event was initially reported as a magnitude 4.4 earthquake.
“Additional analysis of nearby seismic stations, long period seismic waves, and satellite imagery led to the determination that the seismic event was instead a glacial collapse and debris flow, and that no earthquake had occurred.”
Prime Minister Andy Burnham said on Wednesday that the Government will do “everything we can” to support British nationals in Nepal following the floods.
The Foreign, Commonwealth and Development Office said it was “deeply saddened by the loss of life and devastation caused by the floods in Nepal”.
It added: “British nationals in Nepal should follow local authority advice and exercise caution while travelling.
“For consular assistance call (+44) (0)207 008 5000 or (+977) (0)14237100.”
