Police in eastern China told the lawyer of a civil rights activist on Friday that his client was being investigated for alleged incitement of subversion as part of a government crackdown on dissent that started late last year.

Lawyer Peng Jian, who represented Ding Jiaxi, said he was told by police in Yantai, Shandong province, that the 53-year-old activist was officially under investigation and that his request to meet Ding had been rejected.

Ding is being held under “residential surveillance” – a form of secretive detention – and is barred from contacting his family or lawyer. According to Peng, if Ding is finally charged and convicted, he could face a jail term of up to 15 years since it was his second run-in with the law in five years. The activist was sentenced to 3½ years in prison in 2014 for disrupting public order and was released in October 2016.

“He is now held for the second time in five years,” Peng said. “If he is convicted again, he may face a stiff sentence.”

Calls to Yantai police for comment were not answered.

Ding was among a number of dissidents – including Zhang Zhongshun, Dai Zhenya and Li Yingjun – who were taken away by the authorities in the last week of December after attending a private dinner for about 20 people in Xiamen, Fujian province. After the detentions, police searched the flat of Xu Zhiyong, a Beijing-based civil rights activist , and interrogated his girlfriend, Li Qiaochu, prompting him to go into hiding, Xu wrote on Twitter.

Ding was a lawyer specialising in human rights cases before he was jailed and stripped of his licence in 2014. He was also a key figure in the New Citizens’ Movement, a group that advocates working within the system for political change, including urging officials to publicly disclose their wealth.

According to Ding’s wife, Luo Shengchun, her husband has continued his activism to raise public awareness of civil rights since his release in 2016.

Luo, who lives in the United States with the couple’s two daughters, said the rejection of Peng’s request to meet his client had raised concerns that Ding might have been tortured in custody.

“He believes that democracy and freedom are the fundamental human rights of a person,” Luo said.

“I can’t understand – how can a man of such moderate ideas be accused of inciting subversion?” she said. “This shows how fragile the authority is as it cannot tolerate even the mildest, most rational and peaceful expression of civil rights.”

Neither Ding’s family members in China nor Peng have received the official documents notifying them of Ding’s detention or arrest.

Zhang and Dai are also under residential surveillance but Li’s status is not known.

Zhang, a former university lecturer in Shandong, was accused of inciting subversion after police claimed to have found 245 bullets at his home, according to his daughter Zhang Mofei.

Sophie Richardson, China director at Human Rights Watch, denounced the crackdown on the activists.

“If discussing the need for official transparency over a meal is now considered ‘inciting subversion of state power’, then a lot of officials should be investigated as well … To accuse them of serious crimes and deny them the basic rights to a fair trial is a powerful statement about President Xi [Jinping]’s rule,” Richardson said.