China said it will tighten regulations in its rapidly growing online games sector, requiring game operators to enhance socialist values in their games and hire specialized staff to monitor content.

China's Ministry of Culture said in a circular that game operators must re-examine their game offerings for obscene and violent content and limit the number of virtual marriages and player-versus-player combat.

The changes will affect companies such as Shanda Games, and Tencent Holdings.

Over this year, China's online game industry has grown at a rapid pace, the ministry said in a statement late on Wednesday.

But the current product offerings are not up to standard and the cultural content is lowbrow and having a negative effect on the healthy development of the industry, it said.

NetEase's Chief Executive Officer William Ding said in an earnings call on Thursday he was not aware of the full details of the circular, but that the firm is willing to comply.

China's online game industry is expected to grow by between 30 percent and 50 percent this year, with a sales revenue of 24 billion yuan to 27 billion yuan ($3.5 billion-$4 billion). It has more than 50 million gamers.

China has been stepping up oversight of the industry. Earlier this month, another regulator ordered to stop operating World of Warcraft, due to gross violations of regulations.

(Reporting by Melanie Lee; Editing by Jacqueline Wong)