Anonymous online postings are to be banned by a city in China, after residents mounted a successful internet campaign against proposals for a huge chemicals factory.

Internet users will have to provide their real names, backed up by data from their identity cards, when posting messages on more than 100,000 websites registered in Xiamen. Authorities are taking action after thousands of residents of the prosperous southern port city marched through the streets, mobilised by mobile phone text messages and an internet-based campaign.

Protesters used their mobile phones to send text reports, as well as photos and videos, to bloggers and websites in other cities, which posted live reports of the march. The local government has suspended construction of the £700 million chemicals plant, pending an investigation into the potential environmental risk.

Tian Feng, vice-director of the Xiamen Bureau of Industry and Commerce, said that a new law, the Measures for Management and Disposition of Harmful and Unhealthy Information on the Internet, would be announced soon by the city government. “All postings must implement a real-name system. We are the first in the country to do this,” Mr Tian said.

The law obliges anyone who wants to chat online to register using their identity card. Moderators of political noticeboards will be required to use their real names, and anonymous comments will be banned. Messages will be vetted before they are posted.

One government official said that the protest had shown the necessity to control content on the internet. He said: “Those who illegally spread harmful or bad information will be detained or fined.”

Internet censorship is common in China, where the Government employs an elaborate system of filters and tens of thousands of human monitors to survey the surfing habits of its 140 million internet users.

Dozens of outspoken journalists and internet commentators are serving lengthy prison terms after being jailed on charges such as subversion or leaking state secrets. Internet cafés are required to inspect and register the identity cards of all users, but this is not widely enforced, particularly outside the larger cities.

Lian Yue — real name Zhong Xiaoyong — a writer and blogger who posted real-time footage of the march on his website, was swift to comment on the planned crackdown on anonymous postings. He wrote: “The awakening of public power can perform a key influential function in environmental protection. That small step for Xiamen’s citizens should have become a giant leap for the progress of environmental protection in China. Unfortunately, some local Xiamen officials perhaps did not see this as an honour, and subconsciously felt that they had lost face.”

The clampdown seems unlikely to deter those people who dare to criticise the Government online or to voice dissenting opinions, since most are already well known to the police, and their actions are carefully monitored. Those involved in Xiamen were not political dissidents, but ordinary citizens anxious to protect the environment of their pretty seaside town, which has become a winter escape for Beijing’s wealthy, and also the value of their homes.

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