China's major wireless telecom companies, all state-owned enterprises, are coming under pressure to eradicate access to porn through wireless application protocol (WAP) sites on mobile phones.

"The telecom operators collect fees from mobile WAP services and these operators will take most of the profits generated by porn content on WAP sites," Wang Song, an official with the multi-sector Office Against Pornographic and Illegal Publications, told Xinhua. "So the operators should take responsibility (for cutting the links)."

However, most Internet supervisory bodies had no effective equipment to monitor mobile WAP sites, and the manual checks currently employed were slow, Wang said.

Many pornographic sites took advantage of this to flood WAP sites with lewd material that would have been filtered if it had been on the Internet.

China's three major wireless carriers, China Mobile, China Telecom and China Unicom, offer WAP services to about 192 million mobile phone users, more than half of the total Internet users in China.

The China Internet Illegal Information Reporting Center said on Tuesday that it was receiving a growing number of tip-offs about porn WAP sites.

On Nov. 16, the Office Against Pornographic and Illegal Publications announced a crackdown on the creation and distribution of lewd material, which focused on Shanghai, Beijing, Guangzhou, Zhejiang, where many WAP sites are registered.

It ordered local authorities to "fully clean up" such WAP sites and shut down those with "serious violations." The office said the campaign was launched due to concerns over minors having access to pornography.

In a survey of 235 middle school students conducted by the office in north China's Shanxi Province, 173, or 74 percent, had mobile phones and 142 had logged on to WAP sites. Of the 199 senior high school student respondents, 83 percent knew that some WAP sites had pornographic content.

"Children and adults alike can easily log on to such WAP sites," said Li Qiang, a doctor with Chinese Academy of Social Sciences, who has initiated several reports against WAP site service providers.

China Mobile, China's largest wireless telecom operator, has suspended cooperation with more than 460 business promotion partners since Nov. 16 when the crackdown was launched.

On Friday, it announced it would invest 100 million yuan (14.7 million U.S. dollars) in development of new technologies to filter out porn content on WAP sites.

It followed an announcement by the Ministry of Industry and Information Technology, the telecom operator's governing body, that all WAP sites carried by mobile providers would be required to sign information safety management contracts, under which operators were liable to cut any link with lewd material.