As we reported earlier, officials in Nepal are warning of a possible secondary flood risk near the Bhote Koshi river.

The National Disaster Risk Reduction and Management Authority says satellite information from China suggests the river has been "blocked" and that a "lake" has formed near the site of yesterday's flash flood.

In a social media post, it says the information suggests "the lake is in the process of rising and there is a risk of bursting".

It warns residents and rescuers in the lower bank area to "exercise special caution" and stay in safe places away from the river banks.

Why is it so hard to know what is happening in Tibet?published at 15:12 BST

15:12 BST

Laura Bicker
China correspondent

Image source, Reuters

Tibet, which China annexed in the 1950s, is one of the most strictly controlled regions in the country.

It has long demanded greater autonomy and is heavily monitored because Beijing fears any signs of instability such as protests.

That is why orders are now coming personally from the top leader Xi Jinping, and Premier Li Qiang is on site today. It is rare for him to make a visit so soon after a major disaster.

To get into Tibet requires a special visa and it is difficult, if not impossible, for foreign media to gain entry. Trying to contact people there is just as hard.

This makes it very difficult for us to know what is happening and we are relying heavily on reports from Chinese state media.

Pilgrims making their way from Nepal through Tibet to the sacred mountain of Mount Kailash need four separate permits, which includes special permission from the Chinese military.

The Chinese foreign ministry has said 260 of the 558 people missing are tourists or pilgrims. We don't know how many of the remaining are Tibetans, and how many are Chinese people who have moved there to run businesses or work on infrastructure projects.

Moyurie Som
BBC Bangla

We are continuing to hear from families in India waiting for news of relatives caught up in the deadly flash floods.

Among them is the family of Ranajit Kumar Howladar, 63, who is part of a group of 30 tourists and two tour assistants from West Bengal who have been unreachable since 25 August.

Howladar was travelling to Kailash Mansarovar in Tibet, a major pilgrimage site sacred to Hindus and several other faiths.

His wife Gayatri tells BBC Hindi she last spoke to him on Tuesday night. "We just hope he is alive," she says.

Their daughter Sunanda, who has been seeking information from police and the tour operator, says the agency told her two women from the group had been rescued, but could not provide information about the others.

Howladar, a retired railway employee, had waited until retirement to make what his wife described as a "dream" pilgrimage.

As we've been reporting, the US Geological Survey has said flash floods were sparked by a glacial collapse in the mountainous area close to the Nepal-Tibet border.

This resulted in seismic activity and caused "catastrophic" impacts downstream of the Trishuli river, as floodwaters spread into several regions in Nepal.

The Rasuwa district is the closest to the origin of the floods, while the neighbouring Nuwakot district has also been severly impacted.

In its latest update, Nepal police says of the 359 bodies recovered so far, 17 were recovered from Rasuwa and 28 in Nuwakot.

It added that 132 bodies have been recovered in Chitwan, which is where the Trishuli runs its course and flows into the Seti Gandaki river.

Image source, PA Media

King Charles III says he and the Queen are “heartbroken” and send their “most profound sympathy” to those affected by the “devastating” flash floods in Nepal.

“Many in the United Kingdom have strong, deep and personal ties to this part of the world," the British monarch says in a written message.

“We send our most profound sympathy to all those who have so tragically lost their loved ones and we feel deeply for the many families awaiting anxiously the news of friends and relations."

The King also pays tribute to "the police and Armed Forces personnel who lost their lives while carrying out their courageous duty in the service of others".

He adds that "as always, the United Kingdom stands ready to help support those in need".

Azadeh Moshiri
Reporting from Nepal

Here at Kathmandu's domestic airport, we're seeing military support arriving - all part of the effort to find the hundreds who are missing right now.

Families are gathering, waiting for any information they can find.

We spoke to one woman who was in contact with her husband at 08:30 local time (02:45 GMT) yesterday but hasn’t heard from him since. She’s desperate for information.

"My husband had taken the car to pick up a guest," she says, adding that she has come today because she heard that the injured are being brought here after being rescued.

Hannah Roe
BBC South East

In parts of the UK some people with relatives in Nepal are fearing the worst.

"To be honest I believe that they’re not there anymore," says Pramod Poudel, whose wife, mum, uncle and brother have been reported missing.

Poudel, who runs the Mo Mo Nepalese street food company in Sussex, says he knows his father is alive and will be flying to Nepal to meet him.

“We’ve got to accept what happened because it’s obviously not only my family,” he adds.

“When I talk with my friends they reckon about 90% of my village is not there and all of the people have gone as well."

A huge search and rescue operation is underway across Nepal following the devastating flash floods that struck several areas close to the country's border with Tibet.

Nepal's National Disaster Risk Reduction and Management Authority says 9,260 members of the police, army and armed police force have been mobilised to help in the operation.

Here are some of today's pictures from the across the country.

Image source, AFP via Getty Images

Image source, AFP via Getty Images

Image source, AFP via Getty Images

Image source, AFP via Getty Images

Laura Bicker
China correspondent

A lake of rising water has formed at a site along the China-Nepal border prompting fears that it could burst its banks - just as rescuers try to find survivors after yesterday’s landslide.

Chinese search teams in Tibet have spent the day assessing the risk of flooding near Gyirong port after a lake formed near the confluence of Nepal’s Chochen river and the Puruchangpo Zangbo river.

They told state media that stabilising this body of water was a priority to keep rescue personnel on the ground safe.

China’s Ministry of Water Resources has used modelling techniques to estimate how much water is in the lake and now say that with continued rainfall, there is a high risk it could burst within the next three days.

The ministry said it will prepare for a potential breach and provide support for emergency rescue efforts.

Gabriela Pomeroy
Live reporter

Image source, Praneeth Sajeepa

I've been speaking to Kavya Koulagi Jayatheertha, whose uncle Prabhath Sajeepa is missing on a journey to the Kailash Yathra, a sacred pilgrimage for Hindus.

Sajeepa, a US citizen who works for a software company in California and has a wife and two children, was on his first pilgrimage with a group from the spiritual Isha Foundation organisation.

“It has been the most devastating news," Kavya tells me.

The family last had contact with Sajeepa on Monday. They’ve been told he was at the Gyirong border crossing when the flash flood hit the area.

"It has been terrible. I hope he is somewhere safe," his niece says.

"We are hoping for good news."

Image source, Reuters

In the latest episode of the BBC's Asia Specific podcast, presenter Mariko Oi speaks to BBC Nepali journalist Sanjaya Dhakal in Kathmandu about the impact of the devastating floods and landslides that have struck Nepal and neighbouring Tibet.

They discuss the search for survivors, the pressure on hospitals and rescue services, and the arrival of international aid as communities try to recover from the disaster.

The programme also hears from Tom Robinson, a senior lecturer in disaster risk and resilience at the University of Canterbury in New Zealand, who has studied landslides and worked in Nepal.

You can listen to the episode on BBC Sounds here.

Image source, PMO Nepal

Nepal's Prime Minister Balendra Shah has visited some of the areas worst affected by the flash floods, including Bidur and nearby communities in the Nuwakot district.

During the visit he met local officials, security agencies and community representatives to assess the scale of the damage and discuss the response effort.

The prime minister is reported to have instructed authorities to provide immediate support to families displaced by the floods, reopen blocked roads and restore damaged infrastructure as quickly as possible.

He later returned to the capital, Kathmandu, after inspecting affected settlements.

A Nepal police update says the death toll has risen to 359, as of 17:00 local time (12:15 BST).

This comes about an hour after police announced the death toll was 332.

How the BBC verified shocking flood videospublished at 12:34 BST

12:34 BST

By Yi Ma and Paul Brown

Warning: This post contains distressing content

Among the many verified videos of yesterday's flood, two stood out in particular for the sheer devastation they captured.

Both showed a wall of water engulfing a valley near a border crossing between Nepal and China, as people attempted to escape the oncoming deluge.

They were so shocking that some social media users wondered if they were made using AI.

One of BBC Verify’s main responsibilities is ensuring video and images in BBC News output are genuine - and the sharing of AI-generated footage during high-profile incidents is increasingly common.

As part of the verification process, we do a detailed visual analysis. Even as AI-generation becomes more sophisticated, there are still elements it occasionally fails to render convincingly such as human movement, text on signs or basic physics.

We found no such glitches in a frame by frame analysis. All the details matched and made sense when compared to older videos showing the same location - and a comparison of the terrain to satellite imagery confirmed the water was flowing downhill.

We also systematically run all clips through AI-checking software. These tools are not foolproof but both videos returned results indicating no evidence of AI generation.

Laura Bicker
China correspondent

Image source, Reuters

Gyirong port has become the focal point of the disaster for rescue teams in China.

Dramatic footage from surveillance cameras appeared to show the grand building marking the border being swept away by torrents of mud and water as hundreds of people ran for their lives.

The building sat in the deepest of the five Himalayan valleys and had become a thriving hub after an earthquake in 2015 damaged other routes.

It was the main passageway for tourists making their way between Nepal and Tibet. More than 100,000 people passed through in the first half of this year and it handled more than 30% of all Chinese-Nepali trade.

Some social media users in China are questioning why the government decided to place such an important port in a deep valley in a geographically unstable region.

Last year, 17 people were killed after severe rainfall led to a massive mudslide and triggered flash floods.

However, history plays a part especially in a mountainous region where only valleys offer a passageway through the Himalayas between the two countries. For more than 1,300 years this port was used by nomadic herders, Nepali traders and local villagers.

Katie Williams
Live reporter

Image source, Reuters

Rescuers are in a race to find survivors after devastating flash floods hit the Nepal-Tibet border on Wednesday.

The full scale of the disaster is still emerging, but officials say at least 332 people have died in Nepal while more than 900 are missing - the majority foreign citizens.

In Tibet, three have been confirmed dead and at least 558 are missing, according to China's state broadcaster. It is unclear whether the missing figures overlap with Nepal's.

An experienced mountaineer who has previously witnessed flash floods in Nepal tells the BBC he can't believe how "explosive" and "violent" the disaster was.

Two sisters whose parents travelled to the region from Texas tell the BBC they "just love them a lot and want them to come home".

Information on what triggered the flooding has been gradually emerging. Experts now believe "glacial collapse and debris flow" was the cause rather than an earthquake.

And experts say there are concerns about possible "second and third waves", potentially caused by debris in rivers.

Justin Rowlatt
Climate editor

Image source, Getty Images

It is worth noting a parallel with the 2015 Langtang disaster. This latest event also appears to have originated on Langtang Lirung, the mountain above the valley.

In 2015, the earthquake triggered a vast avalanche of ice, snow and rock from the mountain that destroyed Langtang village below.

I was the first journalist to reach the aftermath - at least 215 people had died and the village was almost totally covered in rock and ice.

This latest collapse appears to have come from the north face of Langtang Lirung, rather than the south side involved in 2015.

Justin Rowlatt
Climate editor

It is still very early days and scientists are trying to piece together exactly what happened. Satellite imagery and seismic analysis point to a huge avalanche of ice and rock crashing into the valley and triggering the flood.

It is too soon to determine what role climate change played, although researchers acknowledge it could have contributed.

Rising temperatures are causing mountain glaciers around the world to retreat and permafrost (the frozen ground below) to thaw - potentially destabilising steep slopes by weakening the ice that helps bind fractured rock together.

Scientists say these kinds of high-mountain hazards are becoming an increasing concern across the Himalayas.

Mohd Farooq Azam, a specialist with the International Centre for Integrated Mountain Development (ICIMOD), an intergovernmental scientific institution, said the increasing frequency of hazards in the cryosphere - or the frozen parts of the Earth - "is becoming more visible than ever before.

The pace of change is so rapid that current efforts are struggling to keep up".

We'll bring you more from our climate editor in our next post.

Deluge submerges valley in minutes, video showspublished at 11:43 BST

11:43 BST

By Adam Durbin and Benedict Garman

Verified videos showing the sheer scale of yesterday’s flooding along the Trishuli River continue to emerge on social media.

One video BBC Verify has checked shows an almost incomprehensible deluge of water, submerging buildings and fields near the town of Trishuli in a matter of moments.

Here is what the start of the four-minute video looks like, as the flood begins to surge down the river:

Image source, X

About three minutes later, the water has risen metres and filled the valley:

Image source, X

Azadeh Moshiri
Reporting from Nepal

Image source, AFP via Getty Images

Rescuers are struggling to reach areas struck by flash flooding on the border of Nepal and Tibet.

As we landed, we spotted an Indian plane delivering emergency supplies, which is just some of the aid pouring in.

The region where the disaster happened is popular with pilgrims and trekkers, with tens of thousands of tourists making their way from Nepal to Lake Mansarovar every year.

Survivors are sharing harrowing stories of friends and family swept away by the flood and torrents of mud.

Hydropower facilities have been damaged, and there are fears for the workers inside them, many of whom are now missing.

Experts believe a glacial collapse and debris may have triggered the flooding. There are warnings that some debris washed away into the river systems which could trigger more flooding.

But there is also hope. Rescuers are pushing to reach the hardest-hit areas, and have managed to rescue dozens of people so far.