BEIJING (Reuters) - Germany called for the immediate release of disbarred Chinese lawyer Yu Wensheng, who was arrested in January and charged with inciting subversion, saying all he had done was campaign for democracy and support human rights.

Chinese President Xi Jinping has overseen a sweeping crackdown on human rights activism in China that has seen hundreds of rights lawyers and activists detained, dozens arrested and some handed lengthy prison sentences.

Yu, an outspoken critic of the government clampdown who had worked to defend fellow lawyers who were arrested in the sweep, was disbarred on Jan. 15, days before he was detained by authorities outside his home in Beijing.

Initially charged with “obstructing a public service”, Yu is now being investigated for “inciting subversion of state power”, Yu’s wife, Xu Yan, said this week, adding that the police had also summonsed her in relation to her husband’s charges.

German commissioner for human rights Barbel Kofler said in a statement posted online that the latest developments in Yu’s case were “unsettling” and had increased his concerns about the rights situation in China.

“All Yu Wensheng has done is campaign for democratic reforms in China and support fellow citizens who were harassed for exercising their human rights,” he said.

Yu should be released without delay and granted the civil rights guaranteed in the Chinese constitution, he added.

Asked about Kofler’s statement, Chinese Foreign Ministry spokeswoman Hua Chunying told a regular briefing that China had rule of law and that those who broke the law had to “accept legal responsibility”.

“We resolutely oppose any foreign government or individual trying to interfere in China’s internal affairs. I think this German official has no qualifications or right to demand China release anyone,” she said.

The day before his detention, Yu released a strongly worded open letter in which he called for the deletion of a preamble of China’s state constitution, a section that grants the Chinese Communist Party primacy in leadership.

The letter was the latest in a series of statements Yu had made critical of the party and its leadership, including calling for Xi to be replaced as party leader.

Yu’s case, alongside the surprise disbarring of a second prominent rights lawyer, Sui Muqing, shortly after, have sparked outcry from China’s rights activists and their supporters both inside China and overseas.

Petitions calling for reversals of the authorities decisions for both lawyers have been circulated in instant messenger chat groups and online, each garnering hundreds of signatures.