BEIJING (AP) — Police in central China have detained an AIDS activist who contracted the virus as a boy and whose tireless campaigning for the rights of those with the disease angered local authorities, his fellow activists said Saturday.

Under pressure to end Tian Xi's campaigning, police from his home town of Gulu detained the 23-year-old on Tuesday and first held him at a county hospital before his family lost track of his whereabouts on Friday, the activists said.

Tian traveled frequently between Gulu and Beijing, petitioning officials in the capital to compensate him and others who contracted AIDS through tainted blood supplies. In recent weeks, Tian had obtained official documents in which leaders from Gulu and Xincai county, where the town is located, ordered police to stop his activism, according to the Chinese advocacy group Aizhixing and Sara L.M. Davis, a New York-based activist.

"It seems absolutely clear that this was related to his petitioning," said Davis, who traded e-mails with Tian 10 days ago when he was in Beijing. She has worked with Tian, bringing him to an AIDS conference last year, and described him as "a very impassioned advocate."

Duty officers with Gulu police and the township government reached by telephone Saturday declined to comment.

After ignoring or demonizing people with AIDS for much of the '80s and '90s, the authoritarian government has taken a more compassionate line on the disease and combating its spread in recent years. But people with AIDS still face difficulties in getting treatment and compensation, and authorities from Beijing to the local level remain deeply suspicious of independent activists.

Tian's case is emblematic of China's troubles in dealing with AIDS. Unregulated schemes to buy blood and sell it to hospitals ended up contaminating blood supplies in central Henan province in the mid-1990s.

Tian was a third grader when rough play during primary school left him with a mild concussion and doctors in Xincai county gave him a blood transfusion, according to his blog. A blood test given to him when he got sick in 2004 confirmed he had HIV, and soon afterward he began campaigning for redress.

"Thousands of people have been infected with HIV through blood sales and blood transfusions, and Tian Xi's case is an emblem of this ongoing disaster," said Davis, whose group, Asia Catalyst, offers training and consulting to grass-roots activists.

Among the organizations Tian worked with was Aizhixing, one of the earliest and most effective groups fighting to end discrimination against people with AIDS. Aizhixing's founder, Wan Yanhai, came under harsher police scrutiny and harassment early this year and decided to leave China.

One official document Tian had gotten hold of singled out his relationship to Aizhixing and to Wan, the group said. In another document that Tian described to Davis in a conversation 10 days ago, Xincai county leaders ordered local security officers "take measures to perform ideological education work" on Tian.

Petitioners of varied causes flood Beijing to campaign for redress of local wrongs. Tired of the onslaught, the Chinese government has pressured local governments to stop the flow of petitioners, warning that official promotions depend on compliance.

While petitioning in Beijing in mid-July, Tian was detained and briefly held in a local government office being used as a makeshift detention center — a "black jail" — Aizhixing said.

Another petitioner from Gulu said Tian called him on Thursday around noon and said that he was being held at Xincai's No. 2 People's Hospital, watched by more than 10 police. The petitioner, who would only give his surname, Mei, said that Tian's mother went to the hospital on Friday but neither her son nor the police were there.