Thirty-three people from the UK are among hundreds feared missing following a deadly flash flood near the Nepal-Tibet border.

Flooding and mud slides hit the Rasuaw region in the morning on Wednesday, killing at least 157 people in Nepal and three in Tibet, according to Chinese state media.

Nepal police said 579 tourists are missing – including 466 who are foreign nationals, from 28 different countries.

Prime Minister Andy Burnham said he is in touch with local authorities and “will do everything we can” to support British nationals affected, urging those in the region “to follow guidance from the local authorities and follow our travel advice”.

The UK Foreign Office said it is working closely with Nepalese authorities “following concerning reports of British nationals who are missing” and has encouraged Brits to follow local guidance and “remain alert to the changing situation”.

According to Nepal police, 113 of the missing tourists are Nepalese, and 54 are from the US.

Excursion company Alpine Eco Trek, which offers guided expeditions and tours in Nepal, confirmed to the BBC that it has not been able to establish contact with a group of 12 Britons who were booked on a tour to Mount Kailash, and were in the region when the flash floods struck.

The company said it had made attempts to charter a rescue helicopter but were unable to fly due to poor conditions, and will continue to help with ongoing rescue efforts on Thursday.

According to the company’s travel logs, shared with the Press Association, the age of the missing British citizens ranges from 13 to 65.

Four of the firm’s Nepali tour guides are also missing, PA reported.

The company’s manager Kumar Adhikari said he was in contact with the guides until 08:40 when they were expected to be at Tibet’s immigration office, but their phones were disconnected.

“We were hoping that inside it was safe,” he told PA, “but later the video came from China’s government which [showed] even Tibet’s side was hit by the flood.”

Adhikari said he was “slowly responding to” the families of the Britons but has been unable to give them any updates, adding he has been in contact with the British consulate and forwarded them copies of the clients’ passports.

“I feel so sad. We are just thinking about what to do next…We are in pain at the moment, deep pain.”

Foreign Secretary Ed Miliband said he is “deeply concerned” by news of the flash flooding, and wrote on social media: “All my thoughts are with those affected and with British nationals in the area and their relatives here at home”.

In a joint statement with Australia, the EU, Finland, France, Norway and Switzerland, the UK embassy in Nepal urged British nationals in Nepal to “exercise caution in affected areas”.

The flood hit early on Wednesday in Rasuwa, just north of Nepal’s capital Kathmandu, triggering a landslide.

Preliminary information suggested it was caused by an earthquake, but the US Geological Survey said additional analysis indicated “the seismic energy was instead generated by a landslide.”

It said a magnitude 5.2 seismic event caused by a “glacial collapse and debris flow” occurred near the border at 08:37 local time on Wednesday.

Dramatic CCTV footage showed a wall of water and mud hitting buildings near a border crossing and video filmed from inside a bus in Trishuli captured dozens of people trying to flee a flood surge that was surging through the valley.

Meanwhile Chinese state media outlet CCTV said a mudslide in Tibet’s Gyirong killed three people and left 265 missing, with rescue efforts under way.