Image copyright Getty Images Image caption Four South Koreans are among those missing after the avalanche

An operation to rescue at least six people missing after an avalanche in north-western Nepal has been delayed by poor weather, officials say.

The trekkers were on route on a Himalayan mountain near a base camp in the Annapurna region when the avalanche struck after heavy snowfall on Friday.

Four South Koreans - all volunteer teachers - and at least two Nepali guides are among those missing.

A number of other trekkers were rescued from the site of the avalanche.

Heavy snowfall - as much as 5m (16ft) at the scene of the avalanche - delayed rescue efforts on Saturday, South Korea's Yonhap News Agency reported.

But the rescue mission was set to resume on Sunday, with helicopters and 10 more police officers expected to join the search on Mount Annapurna, one of the highest peaks in the Himalayas.

The avalanche happened at an altitude of 3,230m (10,600ft) about 150km (93 miles) north-west of Nepali capital Kathmandu, officials say.

Image copyright Getty Images Image caption The avalanche happened near a base camp in Nepal's Annapurna region

The missing trekkers, two women in their 30s and 50s and two men in their 50s, are teachers who were staying in Nepal for volunteer work, South Korea's foreign ministry told Yonhap News Agency.

The ministry said five other South Korean members of their group took shelter in a lodge before being airlifted to safety. Some reports suggested a third guide was unaccounted for.

Sandesh Pandey of Jangbogo Tour Nepal, which helped organise the trek, said the four missing people were part of an 11-member team from South Korea.

"They were descending [on Friday] after heavy snowfall stopped them from going higher. The remaining five from the team are moving down safely. The other two did not go up in the trek," Mr Pandey said.

South Korea's government has dispatched an emergency team to assist rescue efforts and help those affected.

In a statement on Facebook, South Korea's President Moon Jae-in said his government "will do its best" to find the missing trekkers.

The president said his thoughts were with the missing trekkers and their families, who have flown to the city of Pokhara and are awaiting updates.

Hundreds of foreign climbers head every year for the Himalayas in Nepal, which has eight of the world's 14 highest mountains, including Mount Everest.

Fatal accidents occur quite frequently. In October 2018, nine climbers died when a violent snowstorm destroyed their camp on a Himalayan peak in western Nepal.

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