Rescuers in the search of four South Korean trekkers and three Nepalis said on Tuesday there was little hope of finding them alive after they were swept away and buried by an avalanche in the Himalayas.

The group was descending near Annapurna base camp approximately 3,230 metres (10,600 feet) above sea level when the avalanche struck on Friday after heavy snowfall.

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"It has been so many days, so it is hard to be hopeful for survival. With our equipment we found signals on the area when the avalanche landed, confirming that there are bodies buried inside," rescue worker Ang Tashi Sherpa told AFP news agency.

Experts say there is a very low chance of survival for those buried in an avalanche for more than two hours.

Rescuers have marked the position where signals from electronic detection devices have been recorded.

Local official Him Bahadur Gurung said nearly 15 feet (4.5 metres) of fresh snow had accumulated in the area.

On Tuesday morning, an 11-member specialised team from the Nepalese army departed by chopper for the site along with South Korean personnel.

"Our focus is to find them. The teams will try to expedite melting of the snow or dig through," said Dan Bahadur Karki, police chief of Kaski district.

"It is still a risky operation but all possible efforts are being made."

Officials estimate that parts of the snow mass could thaw in two weeks if it is sunny but it would take up to a month for most of it to melt.

Six of the missing were part of the same expedition, while one Nepali porter was escorting a different group.

The four foreigners, including two women, were part of an 11-member team of South Korean nationals. Others have safely descended.

Education officials in Seoul said they were part of a team of volunteer teachers working with children in Nepal.

Relatives of the missing Koreans who arrived in Kathmandu on Saturday have also visited the avalanche-hit area.

Thousands of trekkers visit Nepal every year for its stunning view of the Himalayas and routes lined with picturesque villages.

The Annapurna region is particularly popular among tourists, with 172,720 visiting the area in 2018.

A snowstorm killed about 40 people on the Annapurna circuit in 2014, in one of the biggest trekking tragedies to hit Nepal.