The day one sales figure doesn't include a further 1.2 million players whose copies of the dungeon-crawling, monster-infested mouse clicking frenzy were included as part of a World of Warcraft Annual Pass promo deal.

Blizzard's online servers buckled under the pressure as 6.3 million players from around the world got hold of the game during its first week, following a May 15 debut.

Players choose one of five character classes -- barbarian, witch doctor, wizard, monk, or demon hunter -- before setting out to save the world from the forces of evil and carry out the instructions of a mysterious stranger.

Having launched the game in North America, Australasia, Europe, South Korea and Southeast Asia as well as Macau, Taiwan and Hong Kong, Blizzard plans to roll it out at retail in Latin America and Russia from June 7.

Its world premiere for Mac and PC took place the same day as Max Payne 3 debuted on Xbox 360 and PlayStation 3.

Torchlight studio Runic Games, co-founded by two of the original Diablo designers, then chose the weekend of May 18 to run an online public beta test for the upcoming  Torchlight II.