(CNN) -- Despite being allowed to tell her husband he won the 2010 Nobel Peace Prize, the wife of Liu Xiaobo was detained in her apartment in Beijing, China, according to a human rights group and her attorney.

Liu Xia has not been charged with a crime, but "appears to be under a de facto house arrest," said Beth Schwanke, legislative counsel for the U.S.-based group Freedom Now.

She was taken to see Liu Xiaobo in a prison several hundred miles northeast of Beijing, Schwanke said, and tell him of the honor.

Upon hearing he had received the peace prize, Schwanke said, Liu Xiaobo began to cry, and said, "This is for the martyrs of Tiananmen Square."

But upon return to Beijing, Liu Xia was not allowed to leave her apartment, Schwanke said. No one is allowed in, and her telephone is believed to be "destroyed," Schwanke said. Liu Xia has been able to post to some Twitter accounts, said Schwanke, who called the action "absolutely outrageous."

"Brothers, I have come back," said a Twitter post purportedly from Liu Xia. "I have been under house arrest since the 8th and don't know when I'll get to see everyone again. They broke my mobile phone so I can no longer make or receive calls."

"I saw Xiaobo, who learned about his winning the prize in prison on the evening of the 9th," she wrote. "We'll talk about the future later."

Since her husband was named as a 2010 Nobel laureate, Liu Xia has gained 1,000 new Twitter followers.

"Xia can't use her mobile phone anymore," tweeted Chinese dissident Wang Jinbo. "I got in touch through some other means. She can't leave home -- they've tightened the security outside." He said Liu Xia can tweet -- "a little freedom."

"Liu Xia is under enormous pressure," said Dr. Yang Jianli, a member of Liu Xiaobo's defense team and a human rights specialist with Freedom Now. "We hope that world leaders will immediately condemn this shameful act by the Chinese government and urge Liu Xia's immediate and unconditional release."

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Beijing did not comment immediately on the report of Liu Xia's detention, and the official news agency Xinhua was silent on the subject.

On Friday, Liu Xia said she was packing to visit her husband under the surveillance of police officers, who promised to take her to visit Liu Xiaobo Saturday. She said she could not wait to see him to tell him he is this year's peace laureate.

Liu Xiaobo won the prize Friday, but news of the win has been blacked out in China, with no mention of it on Chinese media.

The same censorship applies to Chinese blogs, and authorities have blocked the Nobel Peace Prize section of the official Nobel website.

At least two international television networks -- CNN and BBC -- were blacked out as the Nobel committee announced the winner on Friday, and CNN's reports on Liu remained blacked out for most of the day.

Liu was sentenced in 2009 to 11 years in prison for inciting subversion of state power.

He is the co-author of Charter 08, a call for political reform and human rights, and was an adviser to the student protesters at Tiananmen Square in 1989.

His wife called the Nobel Prize "an affirmation of what he has fought for."

Schwanke said Liu Xiaobo is doing well in prison -- much better physically than when he was held in solitary confinement. Mentally, he remains very strong, she said, adding that this prison sentence is his fourth and "he knows this is necessary to secure democracy and human rights in China."

Freedom Now attorneys, as Liu's international counsel, will leverage international political and legal support while his attorneys in China will continue to work on his behalf in Beijing, she said.

Liu Xiaobo's longtime friend Pu Zhiqiang said the prize may not help Liu right now, but it will have effects for the future.

"In the long run, it will leave a legacy that is sure to help bring democratic reform and freedom to China, that will far outlast Liu's life," Pu told CNN outside the gates of Liu's apartment complex.

The Chinese government was angry at the win, calling it "blasphemy against the peace prize" that could harm relations between China and Norway, where the Norwegian Nobel Committee is located.

"Liu Xiaobo is a convicted criminal sentenced to jail by Chinese justice. His acts are in complete contradiction to the purpose of the Nobel Peace Prize," Chinese Foreign Ministry spokesman Ma Zhaoxu said.

Human rights groups like Amnesty International, world leaders such as U.S. President Barack Obama, and governments around the world all praised the awarding of the prize to Liu, with many calling on the Chinese government to free him.

CNN's Brian Walker and Steven Jiang contributed to this report.