Sherpa guides are leaving Mount Everest’s base camp as part of a walkout following the mountain’s deadliest disaster, as some expedition companies announced that they were cancelling their climbs this season.

American climber Ed Marzec said he saw several Sherpas leaving the base camp on Wednesday and many others packing up their tents. Some were loading their equipment on to a helicopter that had landed at the camp.

“There are a lot of Sherpas leaving this morning, and in the next two days there will be a huge number that will follow,” Marzec, 67, from San Diego, said by phone from the base camp. He said he had already decided to abandon his climb.

Tusli Gurung, a guide who was at the base camp on Wednesday, estimated that nearly half the Sherpas had already left.

The walkout is certain to disrupt a climbing season that is already marked by grief following Friday’s disaster. Sherpa guides were hauling climbing gear between camps when a chunk of ice tore loose and triggered an avalanche. Thirteen bodies were recovered and three Sherpas still missing are presumed dead.

“It is just impossible for many of us to continue climbing while there are three of our friends buried in the snow,” said Dorje Sherpa, an experienced Everest guide from the tiny Himalayan community that has become famous for its high-altitude skills and endurance.

“I can’t imagine stepping over them,” he said of the three Sherpa guides who remain buried in ice and snow.

Seattle-based Alpine Ascents International announced it was calling off its expedition. “We have all agreed the best thing is to not continue this season’s climb, so that all can mourn the loss of family, friends and comrades in this unprecedented tragedy,” the company said on its website.

New Zealand-based Adventure Consultants also said it was cancelling its expedition this season.

Marzec said some smaller companies were hoping to go ahead with their climbs.

Nepal’s government appeared to agree on Tuesday to some of the Sherpas’ demands in the threatened walkout, such as setting up a relief fund for Sherpas who are killed or injured in climbing accidents, but the funding falls far short of the Sherpas’ demands.

After the avalanche, the government quickly said it would pay the families of each Sherpa who died 40,000 rupees, or about $A444. The Sherpas said they deserved far more – including more insurance money, more financial aid for the victims’ families and new regulations that would ensure climbers’ rights.

On Tuesday, the government’s offer was modified to include a relief fund to help Sherpas injured in mountaineering accidents and the families of those killed, and to pay for rescue during accidents on the mountain. The government said it would stock the fund annually with 5 per cent of its earnings from Everest climbing fees – well below the 30 per cent the Sherpas are demanding. Nepal earns about $US3.5 million ($A3.75 million) annually in Everest climbing fees.

The insurance payout for those killed on the mountain will also be doubled to $US15,620 (2 million rupees), the Ministry of Tourism said – far short of the Sherpas’ demand for $US20,800.