Provincial Chinese police have detained at least five people over content posted online that alleged gang-rape and murder at a police-backed brothel.

The detentions add to a long string of cases in which Chinese police have taken bloggers or other Internet users into custody for writing online about government corruption. The events also show how Chinese Internet users have sometimes used the Web to reveal and trumpet injustices, and how the government has worked to control online opinion when it turns critical of authority.

The five people have all been detained on defamation charges in the weeks since text and video accounts of the scandal spread on popular Chinese Web forums, lawyers for two of the detained people said Thursday.

A sixth person, writing on Twitter from a mobile phone early Thursday, claimed to have been taken away by police in the same municipal district of Fuzhou, Fujian province, where the other detentions occurred.

Articles posted online last month gave a mother's account of how a gang member called her 25-year-old daughter, Yan Xiaoling, and ordered her to come out to meet. The woman found her daughter dead in the hospital the next day and was told she had been raped by up to eight people before dying, according to the articles.

Police held a press conference the day after the articles appeared online and were widely re-posted. An official denied any violence or rape and said Yan had died of bleeding caused by a failed pregnancy, according to the state-run Xinhua news agency.

The official also denied any police ties to the gangster or to a prostitution-peddling karaoke joint owned by him, both allegations made in the online accounts.

But within days, police began detaining Internet users they seemed to suspect of writing the online accounts. Police have said that the defamation charges stem from the online materials, Liu Xiaoyuan, a lawyer for one of the detainees, said by phone.

Police also told Liu that his client's case touched on state secrets, Liu said.

Liu and Lin Hongnan, a lawyer for another of the detainees, have both been denied visits with their clients, Lin said. Lin's client has been detained for over two weeks.

"That's a long time," Lin said.

The Twitter user who claimed to have been detained on Thursday had written earlier messages on the service about the rape case, including one that linked to a video of the victim's mother speaking.

Police in the district where the detentions occurred refused to answer questions by phone.

Discussion of the detentions appeared to be monitored in Chinese forums. One Twitter user said all of his posts on the issue were deleted from Douban.com, a popular forum.

The force of online opinion has appeared to steer government action in some cases against Chinese citizens. Last month, a court dropped criminal charges against a young waitress who stabbed a Communist Party official who demanded sex. Talk of the case in online forums had grown widespread and overwhelmingly in support of the woman.

But online speech still faces clear boundaries in China. Dissidents, many of whom write online, are often bullied by police. Authorities also monitor Internet traffic, block Web sites they deem sensitive and require owners of online forums to keep them clear of certain political content.

YouTube has been blocked in China for months, and Facebook and Twitter both became inaccessible last week after deadly ethnic riots in western Xinjiang province.

Another, separate detention last month targeted a Chinese blogger who proposed commemorating the date when Beijing suppressed student protests in 1989, the Chinese Human Rights Defenders advocacy group said in an e-mail on Thursday.

Ning Wenzhong, who blogged under the name "Woodcutter," was sent for one year of re-education through labor last month after posting a call online urging people to lay flowers on Tiananmen Square, the group said, citing Ning's brother.

Hundreds were killed when Beijing ordered the military to clear pro-democracy protesters from its central square on June 4 twenty years ago. China this year stepped up Internet censorship and monitoring of dissidents ahead of that anniversary. It faces another sensitive date this October, when the government will mark 60 years in power.