Kathmandu: Nepal's government on Thursday honoured two climbers who were the first to scale Mount Everest without supplementary oxygen 40 years ago.

Minister for tourism Rabindra Adhikari praised the climbers at a ceremony in Kathmandu. Italian Reinhold Messner and Austrian Peter Habeler reached the summit without use of supplementary oxygen, while others on their team used bottled oxygen.

Until then, all climbers carried oxygen cylinders to aid them at high altitudes where oxygen levels are low.

Since Everest was first scaled in 1953, thousands have reached the summit and hundreds more make attempts every year. Messner has been a strong critic of the large number of people climbing Everest. He suggested many years back that Nepal give the mountain a rest to allow it to recover, but it did not listen. "They decided like this, I cannot change it," he said.