Chinese authorities have in recent weeks imposed strict curbs on the country's multibillion-dollar gaming industry, restricting players under 18 to only three hours of gaming time a week and ordering businesses to remove "sissy" depictions of men from their apps.
Top firms were also ordered by regulators this month to stop focusing on profit and gaining fans, with enterprises that are seen as flouting rules threatened with punishment.
This has come amid a broader rollout of regulation aimed at reining in the country's influential tech sector, including tough new data security and online privacy laws and rules limiting the power of app algorithms to shape users' online activity.
At the same time, the country's Communist government has gone after celebrities and music idols, blaming them for promoting "abnormal aesthetics" and unhealthy values among Chinese youth.
The firms said in their statement that they would not place ads featuring celebrities who had "broken the law or were unethical".
The companies have already stepped up restrictions on minors, with Tencent rolling out a facial recognition ‘midnight patrol’ function in July to root out children masquerading as adults to get around the curfew.
But determined young gamers continued to find ways around the rules, using gaming accounts registered in adults' names -- a practice the companies said on Thursday they would put an end to.