"Running for life from my tent. Unhurt. Many, many people up the mountain," tweeted Romanian climber Alex Gavan who had been preparing to ascend nearby Lhotse, the world's fourth highest peak.

"Huge disaster. Helped, searched and rescued victims through huge debris area. Many dead. Much more badly injured. More to die if not heli asap," he later tweeted.

Today, 17 people were confirmed dead on the mountain and 61 people were injured. Rescue efforts were underway, but heavy snow was initially preventing helicopters from reaching climbers, an official said.

Ministry officials estimated that at least 1,000 climbers had been at base camp or on Everest when the earthquake struck.

Among them were about 400 foreigners, including at least two Hongkongers.

Ada Tsang Yin-hung, a life education teacher at CUHKFAA Chan Chun Ha Secondary School in Ma On Shan, was expected to have reached the base camp on Tuesday, said her former student Juno Lee Chun-lung.

Lee said he had managed to get in touch with a local sherpa, whose brother was with Tsang's expedition team, and the sherpa told him Tsang was safe.

"I'm feeling really worried about Ada's safety," he said. "I hope she is OK. Many friends have also been asking me for her updates immediately after they heard about the earthquake."

It was the second year in a row that Tsang was on the mountain at the time of an avalanche. Last year she was forced to abandon her trek after an avalanche near the base camp killed 16 Nepalese sherpa guides in April, leading to the suspension of all expeditions for that season.

John Tsang Chi-sing, who has been climbing for two decades and has reached Mount Everest's peak twice, was at base camp yesterday with another mountaineering veteran, Xia Boyu, who lost his legs on a previous expedition.

Alpine Adventure Travel, the agency where Tsang was expedition leader, said they were safe.

The duo had climbed 6,189 metre Imja Tse, better known as Island Peak, as part of the training for Everest, according to mountaineering photographer Bryan Ong. They should be moving to lower ground from base camp, he added.

Medics already at base camp for the climbing season were working hard to "save lives", doctor and mountaineer Nima Namgyal Sherpa said on his Facebook page.

"Many camps have been destroyed by the shake and wind from the avalanche. All the doctors here are doing our best to treat and save lives," Sherpa said.

"Right now, it is pretty chaotic and we try to help those injured," Danish climber Carsten Lillelund Pedersen wrote in an email to Danish news agency Ritzau.

He said people suffered head injuries, broken legs and "we have supported one who got hit by a flying stone".

Watch: Video shows Everest camp swamped by deadly avalanche

Norwegian climber Teodor Glomnes Johansen told a newspaper in Norway they were working on saving lives. He was at the base camp that was partly smashed.

"We carry out severely injured people. This is pretty tough and heavy. We do not know whether there will be more avalanches," Johansen told Norway's newspaper.

"All those who are unharmed organise help with the rescue efforts. Men, women and sherpas are working side by side. The job right now is to assist the doctors in the camp here."

Pedersen said he and a Belgian companion were at the Khumbu Icefall, close to the base camp at an altitude of 5,000 metres, when the earthquake hit.

"We are starting to receive the injured, the most severe of them (was a man) with many fractures, who was blown away by the avalanche and broke both legs.

"For the camps closer to where the avalanche hit, our sherpas believe that a lot of people may have been buried in their tents," he wrote on Facebook.

Thomas Frese Carlsen, a Danish schoolteacher who was in Nepal with 12 students from Denmark, said that rumours of another earthquake forced many to sleep out in the open.

"We will sleep outside tonight, on the lawn," he told Denmark's TV2 channel.