Sherpa climbers aided by helicopters resumed a search on Saturday for four missing guides after an ice avalanche swept the lower slopes of Mount Everest, killing at least 12 in the deadliest accident on the world's highest mountain.

Climbers declared a four-day halt to efforts to scale the 8,848-metre (29,029-ft) summit and, while some decided to abandon their mission, others said they would go ahead after talking to their Nepali guides.

All the dead are believed to be Nepali guides.

"I sat and counted 13 helicopter lifts - 12 were dead bodies flying overhead suspended by a long line from a helicopter," Tim Rippel of Peak Freaks Expeditions wrote in a blog.

"Everyone is shaken here at Base Camp. Some climbers are packing up and calling it quits, they want nothing to do with this. Reality has set in."

Shocked relatives wondered how they would cope without the men who take huge risks to earn up to $5,000 for a two-month expedition - around 10 times average annual pay in the isolated mountain kingdom.

"He was the only bread winner in the family," said 17-year-old Phinjum Sherpa, as she waited for the body of her uncle, Tenji Sherpa, at a Buddhist monastery in Kathmandu. "I am shaken now the family has no one to support it. We have no one to take care of us."

The ice avalanche struck a perilous passage called the Khumbu Icefall, which is riddled with crevasses and piled with seracs - massive ice boulders or columns that can break free without warning.

Although relatively low on the mountain, climbers say it is one of the most dangerous points on Mount Everest. There are, however, no safer paths along the famous South Col route first scaled by Sir Edmund Hillary and Tenzing Norgay in 1953.

Around 100 climbers and guides had already passed beyond the Khumbu Icefall to prepare their attempts on the summit. They are safe, but a new path will have to be made to make it possible to continue the expeditions.

Rippel's sherpas had lucky escapes - two had returned to base camp five minutes before the avalanche hit, while two were briefly trapped above the avalanche but managed to make their way down.

The Himalayan Guides, a Nepali hiking group, said six of its sherpas had gone ahead of climbers they were accompanying in order to fix ropes and crack snow and ice to carve out a route, when they were caught and killed by the avalanche.

"Now we are concentrating on the rescue. Once that is over we will hold a meeting and decide what to do next," Bhim Raj Paudel, a member of the group, told Reuters. - Reuters