Clear weather and low winds on Mount Everest on Tuesday allowed at least 20 climbers to scale the peak from the Nepalese side while dozens more were reportedly moving up the icy slopes, an official said.

Krishna Dhungana of Nepal's mountaineering department said initial reports indicated the group reached the world's highest peak early on Tuesday.

Mr Dhungana said there are dozens more who are heading up the slopes and expected to summit in a day or two because of the improved weather.

Blizzard-like conditions in the past weeks had forced climbers to wait at base camp in tents and postpone plans to head up the mountain. An avalanche left a Sherpa guide missing and presumed dead, while two Austrian climbers with him were rescued.

May is considered the best time to climb the 8,850-meter mountain. The harsh weather on Everest allows only about two windows - anywhere from a couple of days to a week - in May when conditions are favourable enough for the push to the summit.

Everest lies on the border between China and Nepal, and most mountaineers climb from the Nepalese side, although many also attempt the northeast ridge route that originates in Tibet. -- AP