A car from the US embassy in Beijing arrives at Beijing Chaoyang Hospital Wednesday, where activist Chen Guangcheng was believed to get a checkup. Photo: AFP

China Wednesday demanded an apology from the US for taking a Chinese citizen "via abnormal means" into its embassy in Beijing, stressing that the country respects human rights and citizens should voice their appeals in a lawful manner.

"It should be pointed out that Chen Guangcheng, a Chinese citizen, was taken by the US side to the US embassy in Beijing via abnormal means, and the Chinese side is strongly dissatisfied with the move," foreign ministry spokesman Liu Weimin said.

According to him, Chen, a native of Yi'nan county, Shandong Province, entered the US embassy in late April and left "of his own volition" Wednesday after staying there for six days.

"What the US side has done  has interfered in China's domestic affairs. The US embassy in Beijing has the obligation to observe relevant international laws and Chinese laws, and it should not do anything irrelevant to its function," Liu said.

"China noted that the US has expressed the importance it attaches to China's demands and concerns and has promised to take necessary measures to avoid similar events," Liu added.

AFP cited an unnamed senior US official as saying Wednesday, "This was an extraordinary case involving exceptional circumstances, and we do not anticipate that it will be repeated."

Escorted by US Ambassador to China Gary Locke, Chen was taken to Beijing Chaoyang Hospital Wednesday afternoon.

In a press statement, US Secretary of State Hillary Clinton said that Chen has a number of understandings with the Chinese government about his future, including the opportunity to pursue higher education in a safe environment.

"Chinese officials further stated that they will investigate reported extralegal activities of local authorities against Chen and his family," Reuters quoted another senior US official as saying.

Analysts noted that people in China agree that human rights should be protected and advocated, and human rights issues can be solved in the country without foreign interference or politicization that only complicate matters.

"The incident is probably a technical mistake made by a junior US diplomat. It is not in the interest of the US if other Chinese petitioners follow Chen's example by swarming into the US embassy. It would bring Washington more problems than it can handle," said Jin Canrong, an expert on US studies at the Renmin University of China.

"So far both countries have been trying to solve the case smoothly before the fourth round of the China-US Strategy and Economic Dialogue."

Chen was arrested in 2006 and later sentenced to four years in prison on charges of damaging property and disturbing traffic. He had tried to help reveal to the press the alleged violent practices of local family planning officers.

In 2007, Chen won the Ramon Magsaysay Award, dubbed as the Asian Nobel Peace Prize. Since then foreign human rights groups or foundations started to pay more attention to him, and Chen has been often mentioned by Western politicians.

The family planning policies, which Chen was fiercely against, have generally been relaxed since its peak years.

Chen might have become a tool for some groups to oppose the Chinese government, Wu Danhong, a law professor at China University of Political Science and Law, said in October amid a campaign to rally support for Chen.

"Chen's attitude toward the local government completely changed after he spent some time in the US as a visiting scholar in 2003. He had been conciliatory but became defiant after he came back," an observer told the Global Times.

Qu Xing, head of the China Institute of International Studies, told the Global Times that Chen's case is an isolated one.

"Public policies are not made to satisfy everyone. Chen holds some different opinions toward certain government policies, but this will not cause him any problem as long as he obeys the law and expresses his demands lawfully," Qu said.

Xuyang Jingjing, Liu Linlin and agencies contributed to this story