Online game operators in Beijing will test a ratings system advising parents on sexual and violent content in their games, ahead of the introduction of government guidelines, state media said Tuesday.

The move comes amid a massive nationwide government crackdown on Internet porn and violence - a campaign seen by some critics as a way for the country's censors to reinforce the "Great Firewall of China" against political dissent.

More than 30 operators have agreed to rate their games according to their suitability for children and adults this month, an official from the Beijing Animation Game Industry Union was quoted by the Global Times as saying.

Gamers will need to provide their identification numbers in order to play, to prove they are old enough to view the content, the English-language newspaper added.

The union's secretary-general, Liu Chungang, said the group's decision was a "self-disciplinary, non-governmental act within the industry".

The culture ministry plans to introduce its own ratings system later this year, the newspaper said.

Culture Minister Cai Wu was quoted by state media in December as saying his ministry had banned 219 Internet games for carrying "lewd, pornographic and violent" content.

The online game market was worth nearly 26 billion yuan (3.8 billion dollars) in 2009, up about 40 percent on the previous year, the Global Times said, citing official data.

Internet use has expanded at a dizzying pace in China.

The country has the world's largest online population of at least 384 million users, according to a new tally released last week by the government-linked China Internet Network Information Centre (CNNIC).

The number of Internet gamers in China stood at 217 million in June, according to CNNIC.