KATHMANDU (AFP) -- Avalanches, heavy snow and poor visibility hampered the search Sunday for four South Koreans and three Nepalis caught in an avalanche in the popular Annapurna region of the Himalayas, officials said

Relatives of the missing Koreans have arrived in Kathmandu alongside several officials sent by Seoul to help with the emergency rescue efforts, Ang Dorjee Sherpa of the Korean Alpine Federation told AFP.

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

"Our team reached the area but could not proceed with their search because of more avalanches. We are exploring ways to move the operation forward," said Mira Acharya from Nepal's tourism department.

Rescuers were working with Korean officials to deploy drones in the search on Monday, said Dilip Gurung of the tourism management committee in Chhomrong, which lies on the trekking route.

"It is difficult for people to go. We will try to fly drones to help find something," Gurung said.

Helicopters were sent out on Saturday to rescue about 200 people stranded around Annapurna and other nearby mountains after the incident.

Guesthouses and the trekking route were blanketed in a thick layer of snow.

"The snow was very deep and it took us more than double the time to dig through and walk," said Jeevan Dahal, a guide who was rescued by helicopter.

"We saw the avalanche-hit area from the helicopter. Everything was white."

Tek Gurung, a guesthouse owner aiding the search operation, said more than two metres of snow (6.6 feet) had fallen on the trekking trails and it was "extremely difficult" to search the snow-covered area on foot.

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

The four foreigners -- two men and 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.

Two more South Koreans were due to arrive in Nepal on Sunday to help with the search, the country's foreign ministry said.

Sherpa said it had snowed heavily around Annapurna in recent days, making the trek risky.

"The weather and snow got worse and, feeling it was becoming dangerous and difficult, they decided to turn. As they were heading back the avalanche hit,"

Sherpa told AFP on Saturday.

Annapurna is an avalanche-prone and technically difficult mountain range with a higher death rate than Everest, the world's highest peak.

Thousands of trekkers visit the route every year for its stunning views of the Himalayas.

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