Liu Xiaobo activists claim they have been assaulted and harassed

Dozens of supporters of Nobel Peace Prize winner Liu Xiaobo have claimed to have been detained, assaulted, harassed or kept from leaving their homes by Chinese officials in the week after the award was made.

The latest appears to be a woman who Liu has said should win the prize: Ding Zilin, who has fought for years for China's government to recognise the hundreds killed in the military's crackdown on pro-democracy demonstrators in Tiananmen Square in 1989.

Liu's wife sent out an alert yesterday that said Ding had "disappeared" and urged people to "pay attention" to her case.

Specially targeted for harassment after Liu won the peace prize are the first group of signers of Charter 08, the demand for greater freedoms that brought Liu an 11-year prison sentence for subversion and that was cited by the Nobel committee.

"I'm so sorry. I have a lot to say, but I don't dare to talk. I've been confronted several times by police already since Liu Xiaobo won the prize," writer Zhao Shiying, who signed Charter 08, said. "Anyone who signed the charter" is getting police attention, he said. "I hope you understand this life we lead."

Some received threatening phone calls from police as they prepared to release an open letter late on Thursday calling for Liu's release, said Xu Youyu, a professor with the Chinese Academy of Social Sciences who signed and helped prepare the letter. He said more than 120 people, including prominent activists and journalists, had signed.

"We call upon the Chinese authorities to approach Liu Xiaobo's Nobel Prize with realism and reason," the letter states. It also asks police to stop "these illegal actions".

"We thought we had to say something," said Xu, who added that he personally had not been harassed. "The government is still doing the same things."

Beijing-based activist Fan Yafeng said he has been assaulted this week by the police who watch him.

China has responded angrily to the award, claiming the West was using it to undermine China and calling Liu a criminal. In particular, Beijing has singled out the Norwegian government for its "erroneous support" of the Nobel Committee's decision, cancelling several meetings with a visiting minister.

Liu Xiaobo, a protester who helped persuade students and other demonstrators to leave Tiananmen Square hours before the military moved in, told his wife he was dedicating the peace prize to the crackdown's "lost souls".

Ding, the activist who founded the group Tiananmen Mothers to fight for the memory of those killed, including her son, had been warned before the peace prize not to give interviews.Her mobile and land phones in Beijing and the city of Wuxi, where she was last heard from, appeared disconnected yesterday.

"The last time I talked to her was 8 October when Liu Xiaobo won the peace prize. We were so happy," Xu Jue, a member of the Tiananmen Mothers, said. "We're really worried she has been taken away. When she was detained before, she would make contact. What if it's worse this time?"

Police in Wuxi yesterday said they would look into Ding's apparent disappearance.

Meanwhile, official pressure continues on Liu's wife, who remains under house arrest.

The law firm that represents Liu said they cannot talk with Liu Xia about the case. Lawyer Mo Shaoping said when he invited her to the law firm to discuss whether to appeal her husband's sentence, Liu Xia said police wouldn't allow it.

Liu Xia, meanwhile, has tweeted that police want to take her out of Beijing, and away from the media attention, on "a tour".