Choppers rescue injured Mount Everest avalanche victims

Helicopters have airlifted injured climbers off Mount Everest after an avalanche killed at least 18 people, even as a powerful aftershock hit the world's highest peak.

At least six helicopters landed at base camp in Nepal on Sunday, AFP's Kathmandu bureau chief Ammu Kannampilly reported after weather conditions improved overnight.

"People being stretchered out as choppers land - half a dozen this morning," Kannampilly said in a text message.

"Weather clear, some snowfall."

Pictures taken by AFP's South Asia photo chief Roberto Schmidt showed an enormous cloud of snow and debris cascading down the mountain as survivors recalled the horrifying moment that disaster struck on Saturday.

"I ran and it just flattened me. I tried to get up and it flattened me again," Singapore-based marine biologist George Foulsham told AFP at base camp.

"I couldn't breathe, I thought I was dead. When I finally stood up, I couldn't believe it passed me over and I was almost untouched."

A spokesman for Nepal's tourism department, which issues the permits to climb Everest, said the death toll had risen to 18 with more than 60 injured.

"Deaths at the base camp have reached 18," Tulsi Gautam told AFP. "Those who are able are walking down. Others are being airlifted to Pheriche."

Ang Tshering Sherpa, president of the Nepal mountaineering association, said the nationalities of those killed was unclear, "but most of them would be foreigners".

Sherpa said there were more than 800 people at different places when the avalanche, triggered by a massive earthquake, struck on Saturday lunchtime.

Fearful climbers again reported smaller avalanches on the mountain, at camp one above base camp, on Sunday after a 6.7-magnitude aftershock hit Nepal.

"Aftershock @ 1pm! Horrible here in camp 1. Avalanches on 3 sides. C1 a tiny island. We worry about icefall team below.. Alive?" UK-based climber Daniel Mazur tweeted.

Many had travelled to Nepal for the start of the annual climbing season, which was cancelled last year after 16 sherpa guides were killed in what was previously the deadliest disaster in the mountain's history.