An Indian climber who reached the summit of Nepal's Mount Everest blamed recent deaths on a lack of oxygen and "proper planning" from the agencies facilitating the expeditions.

Speaking to members of the press in his hotel room, Nava Kumar Phukon reflected on the death of 34-year-old Australian climber Maria Strydom, who he said died in front of him while descending the mountain on Saturday.

Dutch climber Eric Arnold and Indian climber Subhash Paul also died in recent days while attempting to scale the world's tallest peak. 

Two other Indian climbers who had been missing on Mount Everest have been confirmed dead by Nepalese authorities.

The deaths are reported to have been the result of altitude sickness.

But Phukon also emphasised the "lack of responsibility from the agencies".

"They died due to lack of oxygen ... due to lack of proper planning," he said.

As Phukon spoke to the media, Strydom's husband, Robert Gropel, who also took part in the climb and became unwell on the mountain, was waiting in Kathmandu for his wife's remains to be returned there.

Seven Summit Treks, which led the expedition, said that her body is expected to arrive in the capital on Wednesday, an epa journalist reports.

The organisation has defended its safety record following the deaths of Strydom and Arnold, who were both part of the same group.