BEIJING (AP) -- Liu Xia, under house arrest in China's capital since her imprisoned husband Liu Xiaobo won the Nobel Peace Prize, made a rare appearance Tuesday at a trial, yelling out a car window: "I'm not free."

Liu was allowed to leave the Beijing apartment where she has been held for two-and-a-half years to attend the trial of her brother on fraud charges that his lawyers said are trumped up to punish the family. Taken by car to the court in Beijing's suburbs, she sat through the morning-long proceedings, and when she came out accompanied by her lawyer, she shouted from an open window at diplomats and reporters.

"I'm not free. When they tell you I'm free, tell them I'm not," she said.

Her trip to the Huairou People's Court is one of the few instances when Liu has broken the security cordon that has surrounded her. A poet and activist in her own right, Liu became an exponent for democracy and freedom of expression after her husband was jailed in late 2008 for authoring and disseminating a program for political reform called Charter '08.

Liu Xiaobo was later sentenced to 11 years in prison, his fourth prison term in 20 years of political activism. Since he was awarded the Nobel in 2010, authorities have tried to turn Liu Xia into a non-entity to prevent her from becoming a rallying point for Chinese seeking democratic change. She has been allowed out of her apartment once a week to buy food and see her parents and once a month to visit her husband in prison.

Authorities in China routinely put pressure on family members of political activists and government critics to cow them into falling in line.

On her way to the court Tuesday morning, Liu Xia told Hong Kong reporters that the case against her brother was aimed at her.

"They want to break one leg and then break another. But I am demanding to stand up straight and not be afraid," said Liu. She added later: "My heart feels weary because my younger brother is very important to me. Though I am his older sister, he has been taking care of me for so many years."

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The charges against the brother, Liu Hui, relate to a real estate deal in which prosecutors said Liu and a partner pocketed 3 million yuan ($500,000) that was claimed by another party to the transaction.

His attorneys said the funds have been returned and the dispute does not rise to the level of crime. Investigators previously looked into the dispute last year and did not pursue charges, reviving them only in February. In the weeks before that, outsiders — a group of Associated Press reporters and separately five political activists — twice managed to slip past the police and visit Liu Xia in her apartment, embarrassing the security forces.

Being able to leave the apartment for her brother's trial, Liu said, was welcome change from house arrest. "I hope that from today on every day can be like this," she said.