Two more climbers have died on Mount Everest, expedition organisers said Friday, bringing the number of deaths on the world's highest peak this climbing season to nine.

On average, around five climbers die on the 8,849-metre (29,032-feet) mountain every spring.

But this year the toll has reached nearly double that little more than half way through the season.

The area above 8,000 metres is known as the "death zone", where thin air and low oxygen levels heighten the risk of altitude sickness, and it's notorious for its difficult terrain.

A Malaysian and a Chinese climber were confirmed as the latest fatalities.

"A 55-year-old Malaysian climber has died today above Camp 4 as he was descending without reaching the summit," Nivesh Karki of Pioneer Adventure told AFP.

A Chinese mountaineer died on Thursday.

"His death has been reported to us but we are still trying to get more details," said Pemba Sherpa of expedition company 8K Expeditions.

Nepal has issued 478 permits for Everest to foreign climbers this season, which runs until early June.

Since most will need a guide, more than 900 people in total will try to summit.

According to Nepal's tourism department, more than 400 climbers have already reached the top since the route was set on Saturday.

But the week has also seen several deaths.

A 58-year-old Indian woman who said before her expedition that she had a pacemaker died at a hospital on Thursday in Lukla where she was airlifted from the base camp after falling sick.

A Moldovan climber died Wednesday at Camp 4 en route to the top and another Nepali member of a team clearing trash from the mountain died on his return from the summit.

Three Nepali climbers perished last month when a block of glacial ice fell and swept them into a crevasse as they were crossing the treacherous Khumbu icefall on a supply mission.

A 69-year-old US mountaineer also died this month during an acclimatisation rotation.

In 2019, 11 people died on Everest, with four of the deaths blamed on overcrowding on the mountain.