In this photograph taken on May 23, 2013, unidentified mountaineers look out from the summit of Mount Everest.
At least nine Nepalese climbing guides have been killed and five others are missing after an avalanche struck Mount Everest early on Friday, officials said, in the worst accident to hit the world's highest peak.
"We have retrieved nine bodies and rescued seven people," tourism ministry spokesman, Mohan Krishna Sapkota told AFP.
"Five people are still missing," Sapkota added, revising upwards the number of people previously thought to have been trapped in the snow.
The avalanche occurred at around 6:45 am (0100 GMT) at an altitude of about 5,800 metres (19,000 feet) in an area known as the "popcorn field" which lies on the route into the treacherous Khumbu icefall.
Kathmandu-based mountaineering expert Elizabeth Hawley, considered the world's leading authority on Himalayan climbing, said the avalanche was the most deadly single accident in the history of modern mountaineering on the peak.
In 1996, eight people from two expeditions were killed, said Hawley, in a tragedy immortalised in the best-selling book "Into Thin Air".
The accident underscores the huge risks taken by sherpa guides, who carry tents, bring food supplies, repair ladders and fix ropes to help foreign climbers summit the 8,848 metre (29,029 foot) peak successfully.
More than 300 people have died on Everest since the first successful summit by Sir Edmund Hillary and Tenzing Norgay in 1953.