At least 12 Nepali mountaineering guides have been killed after an avalanche swept down a slope of Mount Everest, a tourism ministry official said.
The avalanche is the deadliest in eight years and hit the most popular route to the mountain's peak.
Three guides were injured and up to five people are missing in the first major avalanche on Mount Everest this climbing season.
After an avalanche swept down a slope of Mount Everest killing at least nine mountaineers, helicopters and food have been sent to base camp to take away the dead and help with rescue efforts.
Some mountaineers remain missing on the mountain.
Footage from NBC News at Mount Everest:
An avalanche that swept down a slope of Mount Everest at the beginning of the main climbing season, has killed nine Nepali mountaineering guides, a Tourism Ministry official said.
The avalanche hit the most popular route to the mountain's peak and three Nepali guides were injured and some people may be missing, Tilak Ram Pandey, an official at the ministry's mountaineering department said.
Madhusudan Burlakoti, a senior official at the ministry, said helicopters and rescuers on foot had been sent to the site.
Six local guides have been killed and nine more are missing after an avalanche swept a route used to scale the world's highest peak, a Nepalese tourism official said.
The avalanche hit just below Mount Everest Camp 2 around 6.30am local time, Krishna Lamsal said.
He added that four bodies have been recovered and rescuers are digging two more out of the snow. Nine other Sherpa guides are unaccounted for and believed to be buried in the snow.
All those killed and missing had gone early in the morning to the area to fix ropes for climbers along the route to the 29,000ft summit.
Hundreds of climbers and guides have gathered at the base camp, gearing up for their final attempt to scale Everest early next month when weather conditions get favourable.
Up to five climbers are feared missing after an avalanche swept the slopes of Mount Everest and hit a route used to scale the world's highest peak.
The avalanche hit the area just below Camp 2, according to Nepal Tourism Ministry official Madhu Sudan Burlakoti.
Rescuers and fellow climbers at the base camp are heading to the area to help, and a helicopter is on the way from Katmandu.
Ang Tshering of the Nepal Mountaineering Association said four or five climbers are believed to have been buried and more injured by the avalanche.
Four people, including an Australian tourist, have been killed by an avalanche and 154 people have been rescued after heavy snow and the Mount Everest, Chinese state media reported.
The Nepalese government plans to open an office at Mount Everest base camp in a bid to regulate attempts on the summit more closely, the BBC reports.
The move follows a series of embarrassing episodes on the world's tallest mountain, including a fight between climbers and local sherpas in April.
Officials also plan to monitor "bizarre" record attempts, believing that some feats "don't bode well for the dignity of Everest".
"These days we see people trying to make bizarre records like, for instance, standing on their head or taking off their clothes while on the summit," said Ang Tshering Sherpa, a member of the committee that recommended the new rules.
Further restrictions on littering and helicopter flights close to the mountain are also expected.
Former and current mountaineers will celebrate the 60th anniversary of Sir Edmund Hillary's historic ascent of Mount Everest.
Mountaineers will gather in London to join the sons of the first men to reach the summit at the signing of a newly-released book on the expedition.
Sixty years ago today Sir Edmund and Tenzing Norgay became the first men to reach the 29,028ft (8,848 metres) summit on May 29 1953.
The Queen and the Duke of Edinburgh will attend a reception to mark the anniversary this evening at the Royal Geographical Society where they will watch footage from the time, view an exhibition and meet families and guests.
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An 80-year-old Japanese mountain climber has received a hero's welcome in Kathmandu after becoming the oldest person ever to reach the summit of Mount Everest.
Yuichiro Miura, who has undergone heart surgery four times, was greeted with garlands of flowers and a press pack in the Nepalese capital after reaching the summit late on Thursday.
"This is the greatest feeling in the world," he told family members and supporters gathered in Tokyo, speaking from the summit by satellite phone.
"I never thought I'd get to the summit of Everest at the age of 80. It was the best feeling to get here, but now I'm completely exhausted."
Miura comes from a dynasty of veteran adventurers in Japan, his father having famously skied down Mont Blanc at the age of 99.