Major social game site operators, including Gree Inc. and DeNA Co., have formed a self-regulatory body to improve the way services are provided amid growing concern about child users incurring exorbitant charges.

The Japan Social Game Association, headed by the presidents of Gree and DeNA, said Thursday it plans to draw up new guidelines next month. Site operators will check if games provided by their platforms meet these guidelines while seeking user feedback.

The body, which will cover around 50 companies, including major game developers, will also offer guidance to young users and help firms to cooperate to improve customer support.

"We have received various criticism and opinions on improving the user environment," Gree CEO Yoshikazu Tanaka said at a news conference in Tokyo.

Though the companies have responded through such measures as setting an upper limit for charging users, they should deal with the problems jointly and continuously under a bigger framework, he added.