At least 39 climbers summited Mount Everest via the south east route yesterday, among them Japan's Yuichiro Miura who became the oldest man ever to stand at the roof of the world, Nepal's tourism ministry said.
The two Irish climbers, Mick Murphy and Ger McDonnell, were among 41 who were marking the 50th anniversary of Hillary and Tenzing's first successful ascent in May 1953.
Yuichiro Miura, aged 70 years and 222 days, breaks the record of compatriot Tomiyasu Ishikawa, who summited last year at the age of 65 years and 176 days.
The veteran Miura, also a champion skiier, was part of a nine-man team which included his son Gota, 33. Before they set out they said they would ski from the summit down to Base Camp but there was no immediate news on whether they had carried out their plan, the ministry said.
After weeks of ferocious winds near the summit, the weather suddenly changed on Wednesday night and numerous teams who had been waiting for the break set off for the top. However, the window did not last and the weather closed in again, forcing scores of climbers back down again, mountaineering officials said.
Among those who did manage to scoot to the top of the 8,848 metre (29,028 feet) peak in time was an expedition comprising five Japanese and three Sherpas, the ministry said.
A third team, part of a joint Nepalese and Indian army expedition, however, beat the others to the earth's highest point on Thursday and became the first this year to ascend from the south side, using the route first pioneered by Tenzing and Hillary.
An army spokesman said the team comprised four Nepalese and three Indian soldiers, and seven Nepalese Sherpas.
The 14 climbers had returned "safe and sound" to Camp Four, the high-altitude base from which summit bids are launched, Royal Nepalese Army (RNA) spokesman Dipak Gurung said.
Tourist ministry sources said Alexia Zuberer from Switzerland was the first lady climber to scale Everest this season. She reached the peak Thursday with two Frenchmen, Sebastien Figlioni and Francois Pallandre, and three Nepalese guides.
Two Nepalese Sherpas reached the top of Mount Everest Tuesday.
A total of 25 teams are hoping to conquer the world's highest mountain to celebrate the first-ever climb on May 29, 1953.
Massive celebrations are planned in the Nepalese capital Kathmandu next Thursday.