KATHMANDU (AFP) -- Expedition leaders and guides threatened Monday to cancel all climbing on Mount Everest after the deadliest avalanche in its history as hundreds of Nepalese sherpas paid final respects to their fellow guides.

With heads bowed and many in tears, a procession of mourners filed through the centre of Nepal's capital Kathmandu amid growing anger over compensation levels for those bereaved by Friday's tragedy.

At least 13 people were killed in the avalanche above base camp but the toll is expected to rise.

Accompanied by monks and pick-up trucks bearing the caskets of six victims, the mourners also carried a list of demands that they intend to present to the government, warning all expeditions would be cancelled unless action is taken within a week.

The letter, seen by AFP, calls for a sherpa relief fund to be set up using 30 percent of the fees paid by climbers and says life insurance payments, currently set at $10,000, should be doubled.

The letter also warns against "putting pressure (on the sherpas) to continue this season" which only began last week, adding that "we will not hesitate to protest" if their demands are not met.

The petition was penned after a meeting of expedition leaders, sherpa guides and climbers at base camp Sunday night to discuss how to respond to Friday's disaster, the worst single accident in Everest's history.

In a statement, the Nepal Mountaineering Association said the meeting had agreed on "a seven-day ultimatum to the government to address their demands and threaten to stop climbing if the demands are not met".

The government must provide $10,000 each to the families of guides who were killed as well as those who were injured and unable to resume work, the statement added.

Sherpas have also asked the government to pay the medical expenses of the injured, many of whom are recovering in hospital.

The bodies of 13 guides have been pulled from the snow and another three are thought still buried.

Another nine were rescued from the avalanche, which struck as the sherpas hauled gear for international climbers waiting at base camp below.

Reluctant to climb

Some teams at base camp have decided to pull out of the climbing season this year, while others told AFP they are deciding whether to proceed.

Seattle-based Alpine Ascents International, which lost four sherpas in the accident with another still missing, has decided to cancel its expedition, according to its sirdar (sherpa captain).

"We have lost five members of our team. To respect them, we will not be going ahead with our expedition," said Lakpa Rita Sherpa, who has summited Everest 17 times.

US-based Discovery Channel, which was planning a live broadcast of the first winged jumpsuit flight off the summit, also cancelled an expedition after losing its team of sherpas.

Some sherpas said they were reluctant to climb but felt duty-bound to stay until clients made a decision.

"After such a tragic incident, most of us here don't want to go ahead this season," said Tashi Sherpa, whose team, Seven Summit Treks, lost one guide with two still missing.

"But there is so much investment here, we are not in a position to just refuse," he said from base camp.

The disaster underscores the risks borne by sherpas who ascend the icy slopes, often before dawn and usually weighed down by tents, ropes and food for clients, who pay tens of thousands of dollars.

Some sherpa families are angry about the government's offer of 40,000 rupees (about $400) to pay funeral expenses, calling it disrespectful.

Cancellations will be a significant blow to the impoverished Himalayan country which earns millions of dollars in annual climbing fees.

A senior tourism ministry official told AFP he had not seen the letter but said "the government is positive towards sherpa concerns".

The government has issued permits to 734 people, including 400 guides, for 32 expeditions this season to climb Everest.

Sherpas earn between $3,000 to $6,000 a season, but their insurance cover is almost always inadequate.

Most also receive $3,000 coverage for rescues -- less than the cost of a single helicopter trip from base camp.

"We love the mountains... but a mountaineer could climb at peace if he knew that his family will be taken care of if something happens to him," said Mingma Sherpa, the first Nepali to summit all 14 of the world's peaks above 8,000 metres.

More than 300 people, most of them local guides, have died on Everest since the first ascent by Sir Edmund Hillary and Tenzing Norgay in 1953.