Reuters - The death toll from a powerful quake that struck Nepal on Saturday has risen to 449, most of it in the Kathmandu Valley, police said.

The quake measuring 7.9 is the strongest to hit the country in 81 years. "The number of dead so far is 449," police deputy inspector general Kamal Singh Bam said.

A powerful earthquake in Nepal on Saturday triggered an avalanche on Mount Everest, climbers said, raising fears for those on the world's highest peak a year after another avalanche caused the deadliest incident on the mountain.

Romanian climber Alex Gavan said on Twitter that there had been a "huge avalanche" and "many, many" people were up on the mountain.

"Running for life from my tent," Gavan said. "Everest base camp huge earthquake then huge avalanche."

Another climber, Daniel Mazur, said Everest base camp had been "severely damaged" and his team was trapped.

"Please pray for everyone," he said on his Twitter page.

An earthquake measuring 7.9 magnitude struck west of Kathmandu causing buildings to collapse, killing at least 108 people, injuring more and leaving a pall of dust over the city.

An avalanche in April 2014 just above the base camp on Mount Everest killed 16 Nepali guides. April is one of the most popular times to climb Everest before rain and clouds cloak the mountain at the end of next month.