Nepal's aviation regulator has banned helicopters from conducting "non-essential" flights, including those for sight-seeing, for two months after a deadly crash in the Everest region in which six people were killed.

Five Mexican tourists and the Nepali pilot of a small helicopter operated by the private Manang Air company were killed on Tuesday when their chopper crashed while returning from viewing Himalayan peaks, including Mount Everest.

“Non-essential flights like mountain flights, external load operations (sling flights) and showering of flowers by helicopters (will) be restricted till September,” the Civil Aviation Authority of Nepal (CAAN) said in a Twitter post late on Wednesday.

Nepal, which is in the midst of the annual June-September monsoon season, has formed an investigation committee to find out what caused Tuesday’s crash.

The Himalayan nation, home to eight of the world’s 14 tallest mountain peaks including Mount Everest, has a history of air crashes, as many airlines fly to small airports in remote hills and near peaks often shrouded in clouds.

Nepal's worst air crash in 30 years killed 71 people in January, when a plane went down near the tourist city of Pokhara.