Britons warned of second Nepal flood as new lake threatens to burst banks

At least 362 people have been confirmed dead after a glacier collapse sent a torrent of rock, ice and mud crashing into Himalayan river systems, striking border regions of Nepal and China's Tibet.

Currently, 33 British nationals, including a 13-year-old girl and a 14-year-old boy, remain among the missing, prompting the UK government to pledge £5million in emergency aid.

Nepal's disaster authority issued a notice on Thursday revealing that debris from the initial flood has dammed a river, creating a lake whose water level is steadily climbing and could give way at any moment.

"Residents of the lower banks... passengers, rescuers engaged in rescue operations, and all concerned are requested to exercise special caution and stay in safe places away from the river banks and risky areas," the authority said.

On the Chinese side, officials cautioned that roughly three million cubic metres of water, equivalent to approximately 1,200 Olympic swimming pools, is expected to pour into an already blocked lake over the coming three days, with the greatest risk of a breach anticipated around September 1.

Forecast rainfall over the next week is set to heighten the danger further, according to China's water resources ministry.

"The volume of water is continuing to increase, and so is the risk," Zhu Jinfeng, a hydrology researcher at the ministry, told state broadcaster CCTV.

Prime Minister Andy Burnham described the unfolding crisis as "a devastating picture" and said scenes of destruction were unlike anything witnessed before in terms of scale.

"We are deploying consular support staff to the region so that British nationals will be able to access support 24/7," he told journalists during a visit to South Wales.

Mr Burnham confirmed the Government had offered £5million towards the relief effort and extended an offer to send emergency responders, though he noted this remained a decision for Nepalese authorities.

Among the 33 missing Britons, nine were travelling with tour operator The Trekkers' Society on a pilgrimage to the sacred Hindu site of Mount Kailash.

A further seven UK nationals aged between 18 and 55 were unaccounted for through operator Kailash Journeys.

The catastrophe was triggered by a glacial collapse that registered as a magnitude 5.2 seismic event, according to the United States Geological Survey, which initially mistook it for an earthquake before satellite imagery and further analysis revealed its true nature.

Entire villages were "completely wiped out" in what Bishal Nath Upreti, president of the Nepal Centre for Disaster Management, likened to a "tsunami from the sky".

Destroyed bridges and nearly 25 miles of damaged roads have left helicopters as the sole means of reaching the disaster zone.

Responding to the fresh lake warnings, some rescue teams in Nepal began retreating to higher ground on Thursday. Pawan Koirala, leading a 13-strong team, said as he moved away from the riverbed: "We are here for rescue and don't want to be near the danger zone."

The King and Queen said they were "heartbroken" by the disaster, sending their "most profound sympathy" to those affected. "Many in the United Kingdom have strong, deep and personal ties to this part of the world," the King added.

The Prince and Princess of Wales also conveyed their shock, saying: "We are thinking of everyone caught up in this terrible disaster."

Nepal's tourism board reported 579 travellers missing in the affected area, of whom 466 were foreign nationals.

Among them were 133 Indian pilgrims heading to Mount Kailash, along with 47 Americans, 34 Australians and 24 Canadians.

In neighbouring Tibet, China's Xinhua news agency puts the number of unaccounted-for individuals at 558.

The Foreign, Commonwealth and Development Office urged British nationals in Nepal to heed local authority guidance and travel with caution.