Two more climbers have died on Mount Everest taking the death toll on the world's highest mountain in the past month to at least five amid mountaineers' safety concerns, officials said.

A 54-year-old died on the Tibetan side of Everest, while a 48-year-old Slovakian died near the Balcony in the south in Nepal, officials said. Both climbers died yesterday.

The Australian man died due to apparent altitude sickness about 8,300m (27,230ft) above sea level while on his summit approach, said a company official that coordinated logistics for the climbe

"He fell sick and died while being brought down to a lower camp," he told Reuters in Kathmandu. He said he was unable to give details because of poor communications with the team.

The Slovakian man died at around 8,400m (27,500ft) in the "death zone", on the Nepali side where the air is very thin, a Tourism Department official said today.

He also said the exact circumstances leading to the death were not clear.

A US climber died earlier in the weekend, while contact has been lost with an Indian after he scaled the peak on Saturday.

On 30 April, a famed Swiss climber fell to his death near Mount Everest while preparing to climb it.

 An 85-year-old Nepali man died at base camp earlier this month while trying to set a record for the oldest climber.

This year's Everest expeditions have been confronted by bad weather and high winds.

"There have been deaths on both sides. While few details are provided, it appears these were associated with altitude, not weather," US blogger and climber Alan Arnette said in a post.

Nepal has cleared 371 climbers to Mount Everest in the current season, which ends this month.

Nearly 200 climbers went to Tibet, from where the 8,850m Everest summit can also be climbed. 

Meanwhile, one of the defining features of Mount Everest, the Hillary Step, has collapsed.

It is reported that the step has fallen away due to an earthquake.

Speaking on RTÉ's Morning Ireland, mountaineer Pat Falvey said the Hillary Step is the historical step that Edmund Hillary broke to become the first climber confirmed to reach the summit.

"It is an historical, iconic place for mountaineers around the world," he said.

Mr Falvey said no one can confirm exactly how much has fallen away, and it will depend how the ice and the snow will form there, and loose rocks, if it will make the mountain more dangerous to climb.

Mr Falvey said he nearly died at the Hillary Step when he was climbing Everest in 2003.

He explained that it takes most people 40 to 50 days to reach that point, and mountaineers can get summit fever.

People try to get to the summit from that point because "it is very tempting", added Mr Falvey.