Hundreds of Chinese online game companies have vowed to self-regulate and combat user addiction, the country’s state-backed gaming industry association said, falling in line with a government effort to restrict negative influences from entertainment on China’s youth.

More than 200 companies—among them China’s largest game publishers, Tencent Holdings Ltd. and NetEase Inc. —promised to go a step beyond the playing limits on youth set by China last month, according to the industry association. They agreed to implement controls to prevent young players from circumventing game-time regulations and to weed out harmful and illegal content, the group said Thursday.