Authorities in the southwestern Chinese region of Guangxi have handed down a three-year jail term to an outspoken rights lawyer for "subversion," amid fears for his safety in detention.

The Yulin Intermediate People's Court handed down the sentence to Chen Jiahong on Tuesday after finding him guilty of "incitement to subvert state power."

Chen's ex-wife Luo Fen said Chen, a prominent critic of the ruling Chinese Communist Party (CCP), wasn't present at the sentencing hearing, but was connected by video link from the detention center.

"Chen Jianhong wasn't in court, not in person," Luo told RFA on Tuesday. "He listened to the hearing via video link from the detention center."

She said there are concerns for his safety.

"Chen Jiahong revealed that he had been subjected to beatings by gang members in detention," Luo said.

Chen's former defense attorney Lu Siwei said Chen's outspokenness likely attracted the wrath of the authorities.

"He's kind of a big mouth," Lu said. "In terms of freedom of speech, you should be able to say anything, but lawyers also need to use logic."

"He has a very intense way of speaking and expresses himself through sarcasm, but none of that adds up to a crime," he said.

On China's tightly controlled internet, Chen is known for inscribing the slogan "Set up an assassination detail, liquidate this evil bureaucracy and promote democracy" in Chinese calligraphy and posting it to social media.

"I think the most import factor here was that calligraphy ... I think the police are using it as evidence of criminal behavior," Lu said, adding that no attorney had been present to represent Chen during Tuesday's hearing.

"Lawyers can deal with emerging situations as they arise in court, and they can keep the family members informed," he said. "But the most important thing is for the attorney to meet with and guide the client, and ask if the client wants to appeal."

"Defense lawyers should generally always be present in court, to avoid creating procedural problems," Lu said.

He said Chen had likely cut a deal with the national security police, given the relative leniency of his sentence.

"You plead guilty, and don't engage with them, and they find a way to give you a lighter sentence," he said.

Chen came to prominence in 2015, as police staged a nationwide operation targeting around 300 rights lawyers, law firms and activists.

He was later surrounded by armed police during a standoff relating to the death of Guangxi villager Luo Jibiao, and had his license to practice taken away.