A huge ‌wall of mud and rock has collapsed into a river on the Himalayan border of Nepal and China, triggering catastrophic flooding on the Nepali side that killed scores of people and left hundreds of tourists missing.

In a still-unfolding disaster, verified ‌videos showed dozens of people swept away at the border, with authorities on both sides fearing far higher casualties and massive destruction.

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.

Nepali ⁠police said late on Wednesday that 157 ‌bodies had been recovered so far.

Officials in Nepal said 403 people, including 341 foreigners, were reported missing.

Sunil Sharma, a tourism board spokesman, said 133 were from India on pilgrimage to Mount Kailash in Tibet, a sacred site for Hindus.

Also missing were 47 from the United States, 34 from Australia, 33 from the United Kingdom and 24 from Canada, he said.

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 that eight 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