Under the agreement worked out with the help of U.S. diplomats, Chen Guangcheng is to be allowed to live freely in China and to attend school. Lawyer Teng Biao, however, told The Washington Post the government cannot be trusted.
"The Chinese government has made many promises on many things, but they never keep their promise," Teng said. "They like to punish people afterward."
Zeng Jinyan, wife of another prominent government critic, Hu Jin, said officials threatened harm to Chen's wife and children, The New York Times reported. She said on Twitter, and confirmed to the Times she was the author, and that officials told Chen his family would be forced back to their village and possibly beaten to death there.
But a U.S. diplomat, speaking on condition his name not be used, told the Times Chen had never wanted to remain in the Embassy or to leave China for the United States.
Chen, who fled house arrest April 21, was accompanied by U.S. Ambassador Gary Locke when he arrived at a Beijing hospital for treatment and to be reunited with his family, the Post reported.
It was the first acknowledgment that Chen was under U.S. diplomatic protection in China, a matter that threatened the tenor of U.S.-China relations days before Secretary of State Hillary Clinton and Treasury Secretary Timothy Geithner arrive in Beijing for two days of talks.
Locke called the Post, telling the newspaper he was he was with Chen in a car, stuck in traffic as they made their way to Chaoyang Hospital. Locke then turned the phone over to Chen, who said, "This is Chen Guangcheng."
Beijing's foreign ministry criticized the United States about the incident and demanded an apology.
"It must be pointed out that the United States Embassy took the Chinese citizen Chen Guangcheng into the embassy in an irregular manner, and China expresses its strong dissatisfaction over this," ministry spokesman Liu Weimin said in a statement published by Xinhua, China's state-run news service.
"The U.S. method was interference in Chinese domestic affairs, and this is totally unacceptable to China," Liu said. "China demands that the United States apologize over this, thoroughly investigate this incident, punish those who are responsible, and give assurances that such incidents will not happen again."
A statement issued several hours after Clinton arrived in Beijing said, "Chen Guangcheng has arrived at a medical facility in Beijing where he will receive medical treatment and be reunited with his family."
Chen is not charged with any crime.
In a video appeal to China's Prime Minister Wen Jiabao made after Chen fled house arrest in the village of Shandong, Chen asked that the local authorities who kept him a prisoner in his home for 19 months be investigated and charged, the Post said.
Liu said Chen was in the U.S. Embassy for six days and "left of his own volition."
The spokesman also said the United States must investigate how Chen entered the embassy, hinting that he had help from Americans when entering the secure compound, the Times said.
Chen, 40, has campaigned for the rights of the disabled and the rights of women who were forced to have abortions and sterilizations as part of China's policy of limiting families to one child.