The Korea Fair Trade Commission has launched an investigation into the Korean brand of Blizzard to see if the studio breached South Korea's electronic commercial law. The news comes after Korean, Chinese and Taiwanese players disputed whether Blizzard should take action against players illegally playing the game.

Chinese players were reported to be playing Diablo 3 illegally, which isn't on sale in the region, and they had gained access to Korean servers via proxy. Diablo 3 allows servers from similar regions to effectively act as one, meaning the Korean servers overflowed and caused downtime in the region and elsewhere.

Diablo 3 experienced downtime shortly after launch, as players saw 3003 errors preventing log-in. Some buyers of the game criticised Blizzard for forcing players to be connected to the Internet when playing single-player content.

According to The Wall Street Journal, Korean gamers wanted refunds. Blizzard doesn't issue refunds once the product has been used, but South Korean law does support refunds if the issue was not caused by consumers.

Of the 3.5 million sales in the first 24 hours since launch, and 6.3 million players since, 10 percent came from Korea. Despite being available for digital download, The Wall Street Journal reported "thousands" of Korean gamers queued for the game. Retailers such as Amazon list the title as available, though stock won't return until June 11, 2012.

"It has been a week since the release of the game, and I have been able to play the game around the same amount of time that I have tried to get on the game and [have] been unable to because of the servers being down from errors or from server maintenance," a user review on Amazon UK said.

"According to Gametrics, a research firm on PC games based in Seoul, Diablo 3 accounted for more than 35% of the online PC games played on Tuesday," The Wall Street Journal added. Petitions have reportedly been set up asking for refunds, with one collecting almost 3,500 supporters.

Players also reported hacked accounts, with inventory items and gold stolen despite using the Authenticator app which asks users to provide a unique code once a week. Blizzard since issued a statement on its forums, assuring users hacks did not happen outside of gaining log-in details and urged those who think an account has been hacked to get in touch immediately.