The US Federal Trade Commission sued Amazon Thursday for charging parents for what their children spent on online games without parental authorization. The FTC said Amazon let kids playing online games spend real money from their parents accounts on virtual items — coins, stars and other items used in the game — without getting the consent of the parents. It alleged that Amazon, which sold the apps for accessing the games, did not make clear to parents permitting the downloads that the users would be able to continue spending via in-app charges without controls. The FTC suit cites Amazon internal documents from 2011 and 2012 showing the giant online vendor knew of the potential problem but took no action to stop it.