BEIJING » A Chinese woman was sentenced to one year in a labor camp Wednesday after she forwarded a satirical microblog message that urged recipients to attack the Japanese Pavilion at the Shanghai World Expo, human rights groups said Thursday.

The woman, Cheng Jianping, 46, was accused of "disturbing social order" for resending a Twitter message from her fiance that mocked young nationalists who held anti-Japanese rallies in several cities last month. The original message sarcastically goaded protesters to go beyond the smashing of Japanese products and express their fury at the heavily policed expo site.

Cheng added the words: "Charge, angry youth."

Cheng was seized last month in the southeastern city of Wuxi on the same day as her fiance, Hua Chunhui. Hua, who was released five days later, told reporters the two had planned to marry on the day of their detention.

Under China’s legal system, police can send people to so-called re-education through labor for up to four years without trial. The system, thought to accommodate as many as 300,000 detainees, has been criticized by legal reformers who say it is easily abused. Such labor centers are largely populated by pickpockets, drug users and prostitutes, but they are also used as an expedient punishment for those guilty of political offenses. Once sentenced, people have little chance of appeal.

Widely known by the online name Wang Yi, Cheng is avidly followed by a small coterie of Chinese intellectuals who subscribe to Twitter, which is blocked in China but can be reached by those willing to burrow beneath the government’s firewall. Most recently Cheng sent out messages praising the decision to award the Nobel Peace Prize to imprisoned rights activist Liu Xiaobo. In August, she was briefly detained after expressing sympathy for a detained democracy advocate, Liu Xianbin.

"Sentencing someone to a year in a labor camp, without trial, for simply repeating another person’s clearly satirical observation on Twitter demonstrates the level of China’s repression of online expression," Sam Zarifi, Amnesty International’s director for the Asia-Pacific region, said in a statement Thursday.

Rights advocates said Cheng’s sentence — which may be the first involving a microblog user — highlights the government’s anxiety over social networking services like Twitter and Facebook, which is also blocked here.

Cheng, in some ways, personified that fear.

Renee Xia, the international director of Chinese Human Rights Defenders, said that Cheng was part of a group of daring freelance advocates known as weiguan who travel across the country to show up at courthouses where dissidents are on trial.

Sometimes, when a friend has disappeared into police custody, the weiguan will post to Twitter personal details about the officials involved in the detention. In rare cases, the resulting deluge of phone calls has led to the speedy release of a detainee.

"There is a growing group of people like her, netizens who are moving from cyberspace to the real world," Xia said. "Putting her into a labor camp shows that the government is prepared to come down hard on these people."

Cheng has been sent to the Shibali River women’s labor camp in Henan province, far from her home. Hua told the BBC on Thursday that Cheng, who has high blood pressure, had started a hunger strike in a bid to serve her sentence closer to home.