As well as Xu Zhiyong, a long-time legal campaigner whose case came up for a hearing Friday, and Ilham Tohti, a prominent Uighur economist detained earlier this week, Markus Ederer specifically cited Liu Xia, the wife of jailed Nobel laureate Liu Xiaobo, who has never been charged with any crime but has been under house arrest for years.
"We remain concerned on the overall tightening of the human rights situation and especially about the trials of members of the New Citizens Movement, in particular Xu Zhiyong," Ederer told reporters.
Xu, 40, is one of more than two dozen members of the loosely-connected New Citizens Movement detained after they called for Chinese officials to disclose their assets -- a step seen as a measure against endemic corruption.
Tohti has criticised government policy towards his mostly Muslim ethnic minority, who are concentrated in the far western region of Xinjiang.
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He and his mother were taken Wednesday to an unknown location by several dozen police who seized their mobile phones and computers, his wife Guzaili Nu'er told AFP. The mother was released yesterday.
Ederer said: "I have called on the authorities to treat him in line with Chinese legislation, substantiate the charges, which so far has not happened, inform the family about his whereabouts.
"If these charges cannot be substantiated, release him," he added.
The United States yesterday said Tohti's detention is "part of a disturbing pattern" of arrests of lawyers, activists, journalists "and others who peacefully challenge official Chinese policies and actions".
Responding to the EU and US criticism, China's foreign ministry spokesman Hong Lei said today: "We are opposed to any country or party's accusation against any other country's normal enforcement of law under the pretext of human rights.