Climbers returning from Everest have described scenes of chaos on the roof of the world as 100 people tried to reach the summit of the world's highest mountain within a few hours of each other.

Christian Elde, 37, and Trond Eilertsen, 57, both from Norway, said they had been forced to wait for two and a half hours at crucial points on their final climb to the summit on Saturday as queues formed below steep and technically more difficult obstacles.

"There were people who didn't have much experience, so they were slow on the harder bits and we were standing in queues. If there had been bad weather it could have been very dangerous. It took us a bit over 10 hours to reach the summit and about a quarter of that was spent waiting in a line," Elde, a part-time mountain guide from Oslo, said.

Elde described how he had seen climbers at base camp who were clearly unused to basic mountaineering equipment such as axes and crampons.

"It's a tough mountain," Eilertsen, a lawyer who has now climbed the highest point on every continent on the planet, said. "The oxygen helps, the fixed line [ropes set up to safeguard climbers] helps too but you are still above 8,000 metres and the margins of error there are very, very small. Some people definitely should not have been there."

Both men stressed that climbers in many groups, including their own expedition organised by a British company, had been carefully selected and were highly competent.

The 60th anniversary of the first ascent of Everest by a British expedition in 1953 will be celebrated next week amid continuing concern about inexperienced climbers and overcrowding on the mountain.

More than 700 climbers and guides are expected to attempt to reach the summit this season, which will end within weeks when high monsoon winds make the ascent impossible.

Successful summiteers in recent days included: an Indian former volleyball champion, first female amputee to climb the peak; the first Saudi woman; the first Pakistani woman; a Qatari prince; and a famous Nepalese film star. Many have only recently taken up climbing.

Tashi Tenzing, a three-time summiteer himself, agreed that tensions had been caused by differing levels of experience among mountaineers but stressed that the peak was open to everyone.

"You do get frustrated if you are [held up] behind a non-climber being guided but we all have the right to climb Everest," Tenzing said. He is the grandson of Tenzing Norgay, who, with Edmund Hillary, completed the first ascent of the mountain in 1953.

Among those still hoping to beat the onset of fierce monsoon winds is an 80-year-old Japanese extreme skier, Yuichiro Miura, and his rival for the title of oldest man to climb the mountain, an 81-year-old Nepali, Min Bahadur Sherchan.

Miura was reportedly on Wednesday at the South Col, a windswept shoulder high on the mountain from where climbers try to reach the summit, while his Nepalese rival was at the base camp preparing for his own attempt next week.

On his expedition's website Miura said he hoped "to challenge [his] own ultimate limit" and to "honour the great Mother Nature".

All those who reached the summit in recent days did so using supplementary oxygen. There are now ropes fixed almost the entire distance from base camp at 5,364m up the steep slopes of the mountain to the summit. Guided climbers clip into the ropes at the bottom and follow a well-worn trail through camps which have already been set up for them by sherpas, the local community who have long supplied the specialist manpower for expeditions on the peak. Sherpas also maintain a route through the infamous Khumbu icefall, a massive and very dangerous unstable area of crevasses and ice cliffs which was one of the principal obstacles to early attempts to climb the mountain on the Nepalese side.

The mountain remains risky. An experienced Russian climber was killed earlier this year trying a new route on the south-west face and a 58-year-old Chinese citizen died of altitude sickness on Monday, officials said. Five other climbers have been killed this season and three sherpas.

Last month a high-altitude scuffle broke out between three foreign climbers and sherpas. Sherpas in Kathmandu dismissed the argument as "commonplace".

"I've seen that kind of thing many times. People lose a few brain cells at altitude," said Tenzing, the guide.

Elde, the Norwegian summiteer, said relations between Sherpas and climbers in general had been "superb". He also said longstanding problems with rubbish on the mountain and particularly at base camp appeared largely to have been resolved.