HONG KONG--"We are very sorry, but WikiLib has temporarily suspended service for management reasons," the site announced on its home page.
"Thank you for supporting WikiLib. Please come and visit us another time."
The online user-edited reference runs in China off a server based in the eastern city of Nanjing. It abruptly closed all services shortly after the Lunar New Year holiday, Web users said.
WikiLib uses software called Mediawiki which allows users to contribute to or modify Web content and work collaboratively.
While unrelated, WikiLib's interface is similar to onlinecollaborative encyclopedia Wikipedia and many of the definitions theWeb site lists are direct translations of those found on Wikipedia.
Hubei-based author and member of Independent Chinese PEN Liu Yiming said on Feb. 2 none of WikiLib's Chinese content is available to Chinese netizens.
"I saw the Web site yesterday. It said it had temporarily stopped service. It hasn't closed, but you can't access any of its content," Liu said.
"Maybe they had too much sensitive material on there, and the authorities want to rectify that."
A WikiLib employee confirmed the closure, but denied that political "rectification" was behind it.
"We are now adding functionality to the Web site, including an area for comment and opinion, so we have temporarily halted services," the employee said. "This has nothing to do with political matters."
It is not common practice for Web masters to take Web sites offline in order to introduce new functionality.
An official on duty at the Jiangsu provincial government office for information industry said the person in charge of such matters was not in the office.
Eliminating sensitive content
Liu said a recent crackdown on supporters of an online petition calling for political reforms, Charter 08, was unlikely to be the sole reason for WikiLib's disappearance from the Chinese Web.
"I think that Charter 08 is only one of the reasons behind this. They are probably eliminating all sensitive content; for example the sort of content that gives an account of the [1989] Tiananmen incident, and so on, because that's likely to have caused concern in the government," he said.
"Departments dealing with the news industry have been carrying out rectification of Web sites recently, and cleaning up the more daring ones that they don't like," Liu added.
China has launched a campaign in recent weeks against "pornographic" online material, in a crackdown some see as a veiled bid to filter out politically unwelcome content at the same time.
The authorities have shut down at least 91 Web sites for pornographic and other "vulgar" content, as well as a blog portal frequented by signatories of the politically controversial Charter 08 document.
As well as WikiLib, an MSN forum which had hosted discussions on politically sensitive topics recently was inaccessible in China Tuesday.
'Allow voices to be heard'
Sichuan-based online author Chen Yunfei called on the Chinese authorities to allow people a channel through which to find out what is happening.
"The more you try to stop the public finding out about some things, the more curious they become," Chen said.
"This means that Charter 08 will actually circulate more quickly, not less. I think the authorities should allow different voices to be heard, and let people make up their own minds."
Beijing's latest crackdown on Internet content targeted big names such as Google, Microsoft's MSN, and homegrown market-leading rivals Baidu and Sohu.com.
China's ruling Communist Party is wary of threats to its grip on information and has conducted numerous censorship efforts targeting pornography, political criticism, and Web scams.
Hundreds of dissidents, activists, and former officials have called for dramatic democratic reforms to China 's one-party state in the Charter, which was first published with the names of 303 Chinese citizens as signatories.
Activists now say more than 7,200 signatures have been gathered in support of Charter 08, sparking widespread detentions and interrogations of signatories.
Original reporting in Cantonese by Lee Kin-kwan and in Mandarin by Xin Yu. Mandarin service director: Jennifer Chou. Cantonese service director: Shiny Li. Translated and written for the Web in English by Luisetta Mudie.