Rescue teams Everest
Rescue teams arrive on Everest in the wake of an earthquake, which killed at least 17 on the mountain.Getty

Britons scaling Everest have described their terror as a massive earthquake struck Nepal yesterday, triggering deadly avalanches.

At least 17 are believed to have been killed by avalanches on Everest, after the force 7.8 magnitude earthquake struck on Saturday, April 26.

A number of Britons are missing, as expert UK search and rescue teams arrived to help search for survivors, with more than 2,000 believed to have been killed across the disaster zone.

Among survivors is Bristolian climber Dan Mazur, who is leading a 22 strong team of climbers and staff on an Everest expedition, and described the unfolding disaster on Twitter.

"A Massive earthquake just hit Everest. Basecamp has been severely damaged. Our team is caught in camp 1. Please pray for everyone," he wrote after the earthquake struck at 11.16am local time.

Today he tweeted about terrifying aftershocks at Camp C1, at 19,500 feet.

"12+1 member #Everest BC TV team passed away. RIP. #Earthquake loosed tons of ice down, creating wind blast destroying BC' heart."

"Aftershock @ 1pm! Horrible here in camp 1. Avalanches on 3 sides. C1 a tiny island. We worry about icefall team below. Alive?"

Disaster live blog

London couple Alex Chappatte and her husband Sam, both 28, who are scaling Everest on their honeymoon, are live blogging their expedition and told of the moment an avalanche struck.

"The earthquake hit about 30 minutes after we had crossed the icefall yesterday morning and found our tents. The ground started shaking violently but before we could react Dan [the expedition leader] was shouting "Get out of your f***ing tents, grab your ice axes!" wrote the couple.

"We staggered out to see an avalanche coming straight at us. A blast of wind knocked us down but we were able to get up and run to shelter behind some tents and anchor ourselves with our axes. We focused on keeping an air hole so we could breathe in the powder."

Chris Harling, who is leader of the Adventure Peaks Everest North Ridge 2015 Expedition was on Everest when the quake struck.

"Here in base camp we initially felt minor tremors, then the ground began to feel like jelly as waves passed through the rocks beneath our feet," he wrote on Facebook.

"Climbers appeared from tents all over camp to try to start to comprehend what they were feeling.

"As the movement became more violent I expected the loose and precarious rocky slopes above the camp area to start shedding huge boulders - it was extremely alarming wondering if we were to be buried by rockfall.

"Sure enough, an area of steep cliffs did break off sending car-sized boulders hurtling down only a few hundred metres from our tents. We are still feeling aftershocks hours later."

On the Google Person Finder website, which allows users to post details of people missing following natural disasters, 3,500 people are listed missing.

A number of people listed as missing on the site in the wake of the earthquake have since been in touch with relatives to say they are well, including UK graduate Tara Bradshaw, 24, from Brighton.

Search for missing Britons

As UK expert search-and-rescue teams arrived in Nepal to assist in rescue operations, the adventure holiday firm Intrepid, which organises treks on Everest, said that it was attempting to locate missing groups of tourists.

International Development Secretary Justine Greening said: "The absolute priority must be to reach people who are trapped and injured, and provide shelter and protection to those who have lost their homes.

"Nepal needs our urgent humanitarian assistance."

The Foreign and Commonwealth Office (FCO) has released an emergency number +44 (0) 207 008 0000 for British nationals needing consular assistance to call.

It also says it has offered assistance to local authorities and has advised British nationals in the area to stay "in a place of safety".

#NEPALEARTHQUAKE AT #EVERESTBASECAMP IN TIBET From Chris Harling, Leader, Adventure Peaks Everest North Ridge 2015...

Posted by Chris Harling on Saturday, 25 April 2015