Reporters Without Borders condemned the harassment of two intellectuals Yu Jie and Liu Xiaobo, who were arrested on 13 December and released the following day.
The authorities accuse the two men, who regularly post articles on the Internet, of damaging state security and have warned them to stop writing. Their homes are under police surveillance.
"The harassment and these sanctions demonstrate yet again the Chinese government’s determination to gag dissidents," said the worldwide press freedom organisation.
Yu Jie, arrested at his Beijing home at 6pm returned home the following morning shortly before 9.30am. "Police questioned me about articles I have published abroad," Yu told Reporters Without Borders a few hours after his release.
"The police officers had printed out all my articles. They told me to sign them to confirm that I had written them", he added.
Yu said the authorities had told him that his writing had put him in an extremely dangerous situation. He had only been released on condition that the police, without any official authorisation, copied every document in his computer. Yu’s phone conversations are now regularly cut off and he can no longer go online.
During a visit to France last September, at the invitation of the French foreign affairs ministry, Yu met several human rights organisations, including Reporters Without Borders.
Police on 13 December also arrested Liu Xiaobo and released him the following morning. The authorities warned Liu that his articles "had gone too far". His computer was seized and he has been placed under house arrest. Liu has been arrested on several previous occasions, but this is the first time that his home has been searched and put under surveillance.
The prominent human rights and free expression activist was behind a petition for the release of cyberdissident Du Daobin, that was sent to Chinese Prime Minister Wen Jiabao. Liu also contributed to Reporters Without Borders report "Internet Under Surveillance".
A third reformist intellectual, Zhang Zuhua, was also arrested on 13 December and spent the night in custody. The Chinese poet was one of the signatories last May, with Yu Jie and Liu Xiaobo, of a letter urging the government to apologise for the 1989 Tiananmen Square massacre. Zhang also posts articles online, particularly on his website www.zhendan.cn.