China Mobile, the country's largest wireless carrier, is coming under pressure to shut off access to pornography through its cell phone network.

The move comes as online sites accessible only through mobile phones are becoming a popular new method for distributing porn, since the technology makes it harder for government to track and shut them down.

In the process however, wireless carriers are making extra money off the fees they charge the companies.

"The pornographic websites along with the carriers form an industry chain producing giant profits, escaping government's regulations on the Internet," said Li Qiang, a postgraduate student from the Chinese Academy of Sciences.

Li, a China Mobile user, became aware of the pornography in mobile phones in March this year when he clicked an ad link in a text message that led him to a site containing pornography.

Wireless carriers are the major beneficiaries of pornographic sites, Xinhua reported, citing officials from the Ministry of Public Security.

Carriers charge subscribers for wireless access to the Internet. They also take a cut of the fees for extra items such as pictures and video clips.

Attention has recently been focused on carriers like China Mobile, who are benefiting from the illegal businesses.

Media coverage of the pornographic websites has prompted China Mobile to block access to these sites and scrap contracts with the companies exposed by media reports, a company official said yesterday.

"I can't be more worried wondering what my child will see when he logs online with his mobile phone," said Zhou Yan, a citizen in Beijing.

There are nearly 650 million cell phone users in China, offering distributors of porn a huge and profitable market.

"Profits are the biggest incentive for cell phone websites to carry porn," said Shi Xiansheng, assistant to the secretary-general of the Internet Society of China.

It costs only 1 yuan (14 cents) to register a domain name and 251 yuan annually to rent a storage space of three gigabytes in a server, according to the industry group.

But proceeds from running a website with pornographic content can amount to as much as a thousand times the costs of running it.