In response, the Guangzhou police force said on its official WeChat account on Wednesday that after reviewing security footage and holding interviews, it found no beating or shaming by police officers. Instead, the authorities said, Sun and two other individuals insulted and filmed the police bureau, disrupting public order, so the policemen performed a security check and made inquiries.

Sun told the South China Morning Post the incident took place on September 20, when she went to the Hualin police bureau in Liwan district, Guangzhou, with her client, Li Xiaozhen. They went to the station at about 3pm to request the release of Li’s husband, Zhou Jianbin.

Li and Zhou both have a long record of petitioning the authorities and had been detained multiple times in the past.

While discussing the case with a policeman surnamed Chen, Sun said on WeChat, he threw his ID card at her and claimed that Sun had attacked him. She said a group of policemen then surrounded her, some grabbing her hands while Chen choked her.

At that time, Sun said, a female petitioner who was at the station started recording what was happening, using her phone. She was stopped from doing so, forced to delete her videos and ordered to take off her clothes, Sun claimed.

Sun said she herself was also ushered into a room, where a curtain was hung to separate a corner from the policemen. She, too, was forced to stand in the corner and take off all her clothes, with the police saying they had to check whether she was carrying any dangerous weapons, she said.

“The entire process lasted about 20 minutes, but it felt like a lifetime,” Sun said in her post.

She added that Li, her client, had told her later that she was also forced to strip.

After a few rounds of interrogations, Sun was released just before midnight, she said, then the next morning, she, her colleagues and her family lodged a complaint at Hualin station.

In the following days, she was interviewed by Guangzhou municipal police, but there were no further communications.

“It takes a lot of courage for her to speak up about such a traumatic experience,” Sui Muqing, Sun’s husband and a former lawyer, told the Post. “It’s increasingly a common practice for lawyers to be illegally detained, but I’m not going to keep quiet about my wife’s case.

“There was nothing legal in what the police did to my wife. It was sheer abuse of power,” he said, adding that after seeing the response from the Guangzhou police, the family decided to consider legal action.

A staff member at the Hualin police station refused to comment when the Post called, and demanded to know where it had heard about the case, before hanging up.

An employee at the Guangzhou Lawyers’ Association said it would post developments on its WeChat account. In an article it posted online, the association said it strives to “protect lawyers’ right to legal practice”.

The incident has received great attention in China’s legal community and raised questions about whether the police officers were operating within the law.

Ge Wenxiu, director of Guangzhou-based Lvcheng Dingbang Law Firm, said the officers’ alleged actions – forcing Sun to strip and forcing the petitioner to delete video evidence – could constitute criminal offences. He also pointed out that video recording is a legal activity and ensures individuals’ right to supervise authorities.

“It would be more fair if a third party came forward to rule over the case, instead of Guangzhou police self-checking,” he said. “Furthermore, it is the police’s responsibility to show all the surveillance videos.”

There has been growing public support for Sun on social media. On Weibo, China’s Twitter-like platform, people called for Guangzhou police to release the surveillance footage, the core evidence in the incident.

“Whoever controls the cameras controls the truth,” read one comment. “I believe the lawyer is speaking the truth. Guangzhou police’s claims had no basis or evidence,” said another.

Some also commented on what they saw as the falling credibility of the Chinese police in the eyes of the public, saying people were increasingly losing faith in the authorities.

In China, lawyers face immense challenges, especially those dealing with human rights issues or property conflicts. In December, two Beijing lawyers were beaten by a group of 14 people in front of their hotel in Jingmen, Hubei province, after a hearing in a land acquisition case.