Nine gaming companies, including the creators of Minecraft, Candy Crush and Clash of Clans, are being investigated by the Competition and Consumer Protection Commission.
The consumer watchdog is looking into whether in-game currencies and purchases are in breach of consumer law.
There are concerns some users, especially children, are unable to understand the real-world cost of in-app purchases.
Geoffrey Gray, Commission Member at the CCPC, said they're working to make the online gaming space a safer and more transparent space for all.
“Millions of consumers across Europe play video games many of which are children.
"Consumers should be able to enjoy these games without being misled about costs, pressured into making purchases, or left unclear about their rights.
"This investigation is focussed on ensuring consumers are given clear information, treated fairly, and properly protected when spending money in games".
The CCPC is working alongside authorities across Europe to launch co-ordinated action through the European Commission’s Consumer Protection Cooperation (CPC) Network.
Among the areas under investigation include, in-game purchases, in-game virtual currencies, users' consumer rights when making purchases, transparency around costs, and the fairness of terms and conditions associated with the online games.
The companies under investigation include: Crytek GmbH, InnoGames GmbH, King.com Operations (Malta) Limited, Mojang AB, Plarium Europe S.à.r.l., PLR Worldwide Sales Limited, Riot Games Limited, Supercell Oy, and Ubisoft EMEA SAS.
