A Romanian mountaineer has tweeted a desperate call for help - claiming that many 'badly injured' people caught in the Everest avalanche could die unless helicopters arrive soon.
Mr Gavan tweeted this morning to say that he'd escaped a 'huge avalanche'.
Earlier, a Nepalese official said at least eight people had died on the mountain, though this number looks likely to climb.
Pictures have emerged of what is said to be the Everest base camp in the aftermath of the avalanche that claimed at least eight lives.
The same Twitter account has also tweeted a picture of what it claims is the avalanche as it happened, tumbling down Everest's south side.
A team of Oxfam technical experts carrying equipment to help purify water and provide sanitation are preparing to fly out to Nepal in the wake of today's earthquake.
In a statement, Cecilia Keizer, Oxfam's director in Nepal, said that telephone lines are currently down, while electricity and water have both been cut off.
!Many of the old houses have been destroyed and at least one large apartment block has come down in Kathmandu," she said.
"People are gathered in their thousands in open spaces and are scared as there have been several aftershocks."
Siobhan Heanue, an ABC News journalist, has tweeted photos taken an hour apart showing the scale of destruction in Kathmandu following an earthquake.
The Nepali government has declared a state of emergency in affected areas and appealed for international assistance following a major earthquake, according to the BBC.
At least 758 people are known to have died in today's earthquake in Nepal, according to the country's Home Ministry.
Some 467 of the fatalities occurred in the Kathmandu Valley - one of the most heavily populated regions.
Following a major earthquake in Nepal and subsequent deadly avalanche on Mount Everest, a Foreign Office spokesperson told ITV News:
The Kathmandu earthquake has a decent chance of claiming tens or even hundreds of thousands of lives, according to alarming projections from the US Geological Survey.
The numbers in the graph below are only projections, but it is clear that more bad news is probably on the way.
Another projection suggests that the economic impact of the quake is likely to reach $10bn (£6.6bn) or more.