A human rights lawyer has been detained in China on suspicion of “inciting state subversion”, according to an official notice obtained by his wife weeks after he spoke out for a hospitalised teacher.

Xie Yang — who has previously defended Christians and democracy activists — has not been heard from since he was detained more than a week ago in Changsha city, Hunan province.

Beijing has stepped up its crackdown on civil society since Xi Jinping took power in 2012, tightening restrictions on freedom of speech and detaining hundreds of activists and lawyers.

The police notice, dated Monday and seen by AFP, says 49-year-old Xie has been detained on suspicion of inciting subversion of state power and “picking quarrels and provoking trouble” — a catch-all allegation frequently used against dissidents and activists.

“I am very angry that he has been detained on trumped-up charges,” his wife Chen Guiqiu told AFP from the United States, where she lives with their two children.

His home was also ransacked, according to Chen.

“Anything that could be opened was opened or torn open, even his pillows were ripped apart,” she said, adding that two computers and his safe were missing.

His detention comes weeks after he tried to visit a teacher, Li Tiantian, who friends said was forcibly committed to a psychiatric hospital after expressing sympathy for views questioning Beijing’s narrative over the 1937 Nanjing Massacre.

The historical tragedy is a hugely sensitive topic in China.

Li was believed to have been held after she publicly sympathised with a Shanghai professor who questioned the official number of deaths of 300,000 attributed to the six-week spree of killing, rape and destruction.

Xie was a vocal advocate for the 27-year-old pregnant teacher, who authorities have said was willingly admitted to the hospital.

He tweeted a video in December showing himself outside the local police headquarters holding a poster calling for her release.

Changsha public security bureau declined to comment, while the detention centre and local propaganda department did not pick up phonecalls.

“Xie Yang has participated in almost all the hot-button issues in China,” rights activist Cheng Xiaofeng, who attempted to visit the hospital with Xie, told AFP.

“His actions probably make the authorities very uncomfortable.”

Xie was previously detained for almost two years during the “709 crackdown” targeting human rights activists and lawyers in 2015, when he said he suffered torture.

Another human rights lawyer, Yang Maodong, was arrested last week also on suspicion of “inciting subversion of state power”, according to a police notice shared with AFP. He had been detained in the megacity of Guangzhou since last month.

Yang has been imprisoned repeatedly as a result of his advocacy.

Yang’s wife died of cancer last week in the US, after he was blocked from leaving China to reunite with her.