By Louisa Lim
BBC correspondent in Beijing
Three high-profile intellectuals have been released by police in China after being taken in for questioning.
Dissidents fear a new crackdown on intellectuals
Yu Jie, Liu Xiaobo and Zhang Zuhua were taken from their homes on Monday and held for about 12 hours.
The three men are well-known intellectuals, some of the most critical voices in the public sphere.
Their detention has raised fears that this could be the next stage in a campaign against intellectuals and critics of the government.
A lawyer close to Yu Jie said he had been questioned about activities endangering national security.
His wife, Liu Min, reportedly says she was told by police to stop her husband publishing articles on the internet.
An article written by a well-known thinker within hours of the detentions said that intellectuals were now terrified.
It described recent events as heralding a return of totalitarianism to the mainland.
These detentions could kill any hopes for a period of political relaxation under party leader Hu Jintao.
The campaign against intellectuals was signalled by an article in the party mouthpiece, the People's Daily, accusing them of elitism.
Newspapers and magazines have also been ordered not to give publicity to several well-known intellectuals who are critical of the government, including Yu Jie.