Six Nepalese guides have been killed and nine more are missing after an avalanche swept a route used to ascend Everest, says a tourism official.

Nepal Tourism Ministry official Krishna Lamsal says the avalanche hit just below camp 2 on the world's highest peak around 6.30am local time today.

He says four bodies have been recovered and rescuers are digging two more out of the snow.

Nine other Sherpa guides are still unaccounted for and are believed to be buried in the snow.

All those killed and missing had gone early in the morning to the area to fix the ropes for climbers along the route to the 8,850-metre summit.

Earlier, Ang Tshering of the Nepal Mountaineering Association, said the area where the avalanche occurred is nicknamed the "popcorn field'', which is just below camp 2 at 6400 metres.

Hundreds of climbers, their guides and support guides have gathered at Everest's base camp, gearing up for their final attempt to scale the 8,850-metre peak early next month when weather conditions are favourable.

Guides and climbers have been setting up their camps at higher altitudes as well as fixing routes and ropes on the slopes ahead of the final ascent to the summit in May.

Nepal this year announced several steps to better manage the flow of climbers, minimise congestion and speed up rescue operations. The preparations included the dispatch of officials and security personnel to the base camp located at 5300 metres, where they would stay throughout the spring climbing season that ends in May.