Shares of Chinese video game companies plunged after the government unveiled plans to control the number of online games as part of an effort to prevent myopia among children.

The plan is the latest move to tighten government oversight over the country's highly popular video game industry — and a new blow to their stock market fortunes. The new regulations were announced after Chinese President Xi Jinping issued an "important directive" to protect children's eyesight. The education ministry said that the authorities will regulate and control the total number of games and new titles.