By Louisa Lim
China is expanding its censorship controls to cover text messages sent using mobile phones.
China wants to keep tabs on the spread of information
New regulations have been issued to allow mobile phone service providers to police and filter messages for pornographic or fraudulent content.
But analysts fear the real targets are political dissidents.
China's authorities are gradually tightening control over the spread of electronic information, particularly on the internet.
A Paris-based group, Reporters Without Borders, says the Chinese authorities are increasingly using new technology to control information.
It says one Chinese company marketing a system to monitor mobile phone text messages has announced it is watching for "false political rumours" and "reactionary remarks".
Venus Info Tech Ltd said in a press release that its surveillance system worked by filtering algorithms based on key words and combinations of key words.
Certain key words could trigger an automatic alert to the police.
Text messaging has already threatened Beijing's control over information.
Last year, the authorities tried to hide the outbreak of the respiratory disease Sars.
But millions of text messages were sent, alerting people to the virus and exposing the government cover-up.
So far, the new regulations are only being used by one of the country's two mobile phone operators, China Mobile Corporation.
But it controls 65% of the mobile phone market, so these new rules will almost certainly become the industry standard.
Last year, Chinese people sent more than 220bn text messages, more than half of all messages sent in the world, according to China's Xinhua news agency.