A Nepalese "Super Sherpa" conquered Mount Everest for a breathtaking 19th time on Thursday, breaking his own previous world record in a climb he dedicated to environmental awareness.

Apa Sherpa, 49, reached the summit of the world's highest peak early in the morning, Jitendra Giri, of the Nepalese government's mountaineering department, told AFP.

"He reached on top of Everest this morning and spent around half an hour on the summit," Giri said, adding that he was in good health and already heading back to base camp.

Apa unfurled a banner that read "Stop Climate Change, Let the Himalayas Live!," after reaching the 8,848-metre (29,028-foot) summit.

"When I talked to him on a radio, he said it was very windy on the top but that the weather was stable," Dawa Steven Sherpa, team leader of the 40-member Eco Expedition, told AFP by telephone from the Everest base camp.

Apa, who bagged his first Everest summit in 1990, climbed the mountain to focus global attention on climate change and its impact on the Himalayas.

Climbers have been reporting the steady break-up of the Khumbu icefall, a treacherous maze of cliffs and crevasses that guard the southern approach to the peak. Many blame increasing temperatures for the changes.

"We are very excited and happy with Apa's achievement. It will highlight the effects of global warming on Everest and other Himalayas," said Dawa.

"Climbing Everest is getting more difficult and dangerous every year because of the melting ice. The rocks that used to be covered by snows are getting exposed."

Apa's expedition team has been collecting garbage from Everest as part of their campaign to return the mountain to a pristine condition.

"We have brought down over five tonnes of mountain trash including parts of a crashed helicopter, old ropes and tents, ladders, metal cans and climbing gear," said Dawa.

The summit season on Everest begins in late April and May when a small window between the spring and summer monsoon offers the best conditions for making the ascent.

More than 100 climbers have already made it to the top this spring season, in which 29 expedition teams are in action.

Apa's successful climb coincided with that of British adventurer Sir Ranulph Fiennes, who reached the summit on his third attempt just before midnight GMT on Wednesday.

Since it was first climbed in 1953 by Edmund Hillary and Tenzing Norgay, the mountain has been conquered more than 3,000 times.