At least 403 people are missing after devastating flash floods swept through the Nepal-Tibet border, including 34 Australians, according to the Nepal Tourist Board as reported by Press Association.

Of the missing, 341 are foreign nationals, with 203 men and 200 women. The nationalities include 47 from the US, 34 from Australia, 33 from the UK, and 24 from Canada.

Among them is one Australian who was travelling with Kathmandu Holiday Tours + Travel, according to Agence France Presse. Australia's foreign minister, Penny Wong, said the government was urgently working to confirm the welfare of Australians in Nepal.

In a statement issued on Thursday morning, she said: "The loss of life and destruction caused by flash flooding in Nepal and China is devastating. Our thoughts are with the loved ones of those killed or missing and all affected by this disaster. Dfat officials are urgently working to confirm the welfare of Australians in the area."

The Department of Foreign Affairs and Trade (Dfat) said it is aware of a number of Australians in the affected area and stands ready to provide consular assistance. A Dfat spokesperson said: "We extend our deepest sympathies to those affected by the significant flooding in Nepal and Tibet, China. Australians in the affected area should follow the advice of local authorities. We are aware of a number of Australians in the area and Australian officials are urgently working to confirm their welfare. We are liaising with local authorities as well as tour operators."

Earlier, Australia's ambassador to Nepal, Simon Ernst, said he was "deeply saddened" by the disaster. In a joint statement issued by the embassies of Australia, Finland, France, Norway, Switzerland and the UK in Nepal, posted on social media by Ernst, they said: "We are deeply saddened by the devastating flooding in Rasuwa and Nuwakot districts and surrounding areas. Our thoughts are with all those affected by this disaster. We express our solidarity with the people of Nepal during this difficult time. We encourage all those in affected areas to follow the guidance of local authorities and official safety advisories as the situation continues to evolve."