Three climbers and a guide have died on Mount Everest, taking to eight the number killed in a week as record numbers tackling the world’s highest mountain have caused dangerous crowding.

More than 120 climbers scaled Everest on Thursday, but some were caught in the crowd of people on the slopes, leading to exhaustion, dehydration and death, Nepalese officials said.

The death toll so far this season outstrips the five killed in the whole of last year.

“Traffic jams” of climbers have formed near the summit this year after about 380 permits to climb were issued. Last year Nepal issued 365 permits for expeditions to Mount Everest; in 2016 it was 289.

Two women and a man from India died of exhaustion while descending from the 8,850 metre (29,035 feet) peak.

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They were Anjali Sharad Kulkarni, 54, Kalpana Das, 49, and Nihal Ashpak Bagwan, 27.

A tour organiser said Bagwan had been “stuck in the traffic for more than 12 hours and was exhausted”.

Others who were killed this week included a 65-year-old Austrian climber, who died on the northern Tibet side, another Indian and an American.

A member of a Swiss team died high up on the Tibetan side on Thursday, according to Everest blogger Alan Arnette, who cited a Swiss operator, Kobler & Partner. The climber’s name has not been released.

An Irish professor, Seamus Lawless, has not been seen since falling on 16 May.

A total of 17 climbers have died or are missing on different Himalayan peaks in Nepal, seven of them Indians, since the start of the climbing season in March.

“The winds have returned, plus the routes are extremely crowded on both sides, due to few summit weather windows this spring,” Mr Arnette said on his blog.

The American who died, Don Cash, 55, had fulfilled his dream of climbing the highest mountain on each continent when he conquered Everest.

“When he was on the top he just fell. The two sherpas who were with him gave CPR and massages. After that he woke up, then near Hillary Step he fell down again in the same manner, which means he got high altitude sickness,” said Pasang Tenje Sherpa, head of Pioneer Adventure, which provided the guides.

Altitude sickness, caused by low oxygen at height, causes headaches, vomiting, shortness of breath and mental confusion.

Agencies contributed to this report