At least 10 people have been reported killed after an earthquake triggered a "huge avalanche" which swept through Everest base camp.
Hundreds of people have been killed in Nepal after a magnitude 7.9 earthquake toppled buildings.
Romanian mountaineer Alex Gavan said there had been a "huge disaster" on the world's highest peak and pleaded for rescue helicopters to be sent before more of the injured died.
"Helped searched and rescued victims through huge debris area. Many dead. Much more badly injured.More to die if not heli asap," he tweeted.
Earlier he described "running for life from my tent" as the avalanche hit.
Images from Everest showed belongings scattered on the ground and snow covering tents.
Arjun Vajpai, who filmed himself at one of the camps on the moutainside, said there had been "a big few avalanches".
"From here we had quite a bit of rockfall," he said.
"Most of our team is okay, we are doing well, some of our team members just moved up today towards camp one and camp two. We still do not have any report from them, we are trying to get in touch with them."
A Nepal tourism official said part of the Everest base camp was buried.
"We don't have the details yet, but 10 have been reported dead so far, including foreign climbers," Gyanendra Kumar Shrestha said.
Captain Tim Bradshaw, who is leading a British Army team climbing the world's highest peak, told Sky News his tent started to "rock and move" as the earthquake hit.
"Then almost like thunder huge boulders started to break around us from the side of the mountain and roll down towards the bottom, towards base camp," he said.
"Everyone here is fine ... but we are on the other side of the mountain away from the Nepal side, quite away from the epicentre."
Ang Tshering of the Nepal Mountaineering Association said that the avalanche apparently happened between the Khumbu Icefall, a rugged area of collapsed ice and snow, and the base camp.
About 700 climbers are in the Solukhumbu region that includes Everest and about 300 of them are believed to be at base camp.
"We are trying to reach them to see if they are safe, but the phones are not working," deputy superintendent of police Chandra Dev Rai said.
