In one photo, a group of seven men are seen at night holding a white banner with black handwritten characters. "What crime has Liu Yuandong committed when protesting against the nuclear test?" the banner said. "We ask the authorities to release him without charges."  

One photo, dated April 7, shows three men holding a red banner that reads: "Release Liu Yuandong, stop political persecution." Another shows a man named Yu Gang calling for Liu's release outside a Shenzhen subway station. 

Liu’s arrest came 11 days after North Korea conducted its third nuclear test on February 12. Within several hours of Pyongyang’s rocket launch, news of the earthquake triggered by the test close to the Chinese border led to an outpouring of concern in China over nuclear contamination.

The trained chemist gathered some 16 others in Guangzhou, where they held banners condemning the test, according to another person surnamed Liu who participated in the February 23 protest.

Liu Yuandong was first held for 15 days; eight others were also detained, for seven to 10 days; and seven escaped the authorities.

"They didn't let us sleep," said the other detainee surnamed Liu. "They treated us like dogs and pigs."

Liu, who runs the Guangdong-based company Dongsheng Biotech, was detained longer on charges of embezzling corporate funds at his small high-tech company. On April 3, his family was informed of his formal arrest. He is understood to be currently awaiting trial.

"He has not embezzled any money from his own company," Ou Longgui, 28, who has worked at Dongsheng Biotech for years, told the South China Morning Post. "They just used it as an excuse to prosecute him."

Ou, who also participated in the protest, said Liu organised one of the first public protests in Guangzhou in 2011.

"On August 28, 2011, we organised a protest at the Teemall Plaza in Guangdong to celebrate the fall of [Libyan leader Muammar] Gaddafi," Ou said. "This was the first protest for democracy there since 1989."

"Liu said we had to bring the protest from the internet to the public squares," Ou said. "He brought a loudspeaker."

"We were very naïve. We thought we could just show up and get the crowd to walk with us. But within minutes we were surrounded by police."

The dozen people participating in the protest were arrested, but released by the evening, Ou said. "We told the state security officials that Gaddafi was an evil man, and we just wanted to celebrate his downfall," Ou said.

“Liu is a core person among a group of 20 to 30 people in Guangzhou," said the other protester surnamed Liu. "This has nothing to do with religion; he opposes the Chinese political regime," she said. "He thinks the current regime has not been established democratically, has no legitimacy."

Liu Yuandong, a married man and father of two, is a native of Meizhou in eastern Guangdong. He has participated in several protests in Guangdong after the initial anti-Gaddafi protest.

Earlier this year, he participated in a protest in solidarity of the Southern Weekly journalists in Guangzhou in January and the trial of policeman-turned-activist Wang Dengchao in Shenzhen in February.  

On February 16, he participated in a protest against North Korea’s nuclear test in Guangzhou. Others where arrested, but not Liu, whose turn came on February 23.

"Most of us are in Guangzhou," Ou said, "but there are people in other cities. Around Spring Festival we even talked about founding a party, but we have no leaders or even a name yet."

"We thought we'd call it Democracy Action Group [minzhu xingdong pai],” he said. "We will continue to protest, because it's right."