Nepal rescuers race to reach any survivors in tunnels

Rescue teams are racing to reach dozens of workers believed to be trapped inside hydropower tunnels in Nepal's mountains, offering one of the last hopes of finding survivors a week after a Himalayan flood killed more than 1200 people.

The flood, triggered by the collapse of a glacier near Nepal's border with China, devastated towns and valleys across the mountainous region. By Wednesday, at least 1204 people had been confirmed dead and more than 4200 remained missing.

Rescue efforts have increasingly centred on hydroelectric project tunnels where authorities believe workers may have survived after being cut off by floodwaters and debris.

Some tunnels contain chambers with air supplies, and rescuers were trying to reach about 900 missing workers.

"We are very confident that there is life in there because ... there is food and water in the building, that was likely built for communication purposes and as a resting place," Amshu Kiran Shahi, a board member of the Nepal Electricity Authority, told Reuters.

The chance of finding survivors elsewhere was fading, authorities said, but there was no let up in rescue operations as teams scoured the mountainside along the border with China where floods tore through towns and valleys.

"The hope of finding survivors is decreasing," said Phanindra Paudel, a senior official at Nepal's National Emergency Operation Center.

Prime Minister Balendra Shah told parliament the search would continue.

"Our priority remains clear: To continue our search and rescue operations, find those who are still missing and continue supporting everyone affected," he said.

Major rescue operations were under way or planned at four hydropower projects. Two sites, where about 90 people are missing, offered the strongest prospect of finding survivors because of the presence of air inside the tunnels, Shahi said.

At Trishuli-3A, officials believe there was a dry chamber inside and expected oxygen to be flowing through the tunnel, with pipes also being used to push oxygen inside, Shahi said.

Specialised rescue teams from India, China and the United States were involved in the tunnel rescue attempts.

Across the border in Tibet, China raised its death toll to 21, with 541 others still listed as missing.

The update came after Beijing fully reopened the road leading to the Gyirong border crossing, which was obliterated by the giant wall of water and debris that crashed through the area, allowing heavy machinery to reach the core disaster zone for the first time.