According to a 54-year-old prisoner at the Jixi labour camp in the northern province of Heilongjiang in China, guards forced him to play games on the internet to build up credit that they traded for real money, a practice known as ''gold-farming''.
In several online games, including the popular World of Warcraft, players spend hours accumulating gold inside the game, which can then be sold to other players who do not have the time or patience to earn their own online currency.
Though technically illegal, the practice is said to be widespread with players from developing countries typically selling their gold to players in the US or Europe.
The prisoner who was being interviewed by the Guardian newspaper said online gaming was a far more lucrative activity for the managers of the labour camp than the physical labour the inmates were forced to do.
He added prison bosses made more money forcing inmates to play games than they did forcing the inmates to do manual labour. He added there were 300 prisoners who were forced to play games. He added the inmates worked 12-hour shifts in the camp.
He said he heard the guards say they could earn 5,000-6,000rmb (£470-570) a day, however the inmates never got to see any of the money.