Up to 100,000 people in China and Vietnam are playing online games to gather gold and other items for sale to Western players, suggests a report. The global market for such virtual game goods is worth at least $3bn (£1.8bn) estimates the World Bank study.

About 75% of that comes from so-called "gold farmers" who stockpile game currencies to sell on later. Encouraging these in-game services could aid development in many poorer countries, said the report.

Popular online games such as Lineage and World of Warcraft revolve around the gear that players gather to outfit their characters. Better equipment makes characters more powerful.

Some of that equipment can be found on monsters, as well as being bought from other players who have found or made it.

Increasingly Western players who have limited time for gaming are buying game cash, gear and high level characters from people in China and Vietnam that are paid to play as a job. About a quarter of all players of massively multiplayer online games spend real money on virtual items, suggests the report. Some pay significant sums, with one player splashing out almost 5,700 euros (£5,000) on a single account.

This has led to some of the biggest suppliers becoming substantial businesses, it said, despite the efforts of many game studios to snuff out a trade that they believe undermines the game.

This suggests that the virtual economy can have a significant impact on local economies despite its modest size