Wu, 44, who has been in custody for more than two years, was known for campaigning on issues deemed politically sensitive by the authorities, sometimes using street performances to draw the public’s attention.

Human rights monitors said that his cyberactivism and eye-catching protests were probably seen as a greater threat than the work handled by rights lawyers, who tended to focus on helping their clients with legal issues.

“He became so popular among the grass-roots activists,” Patrick Poon, a Hong Kong-based researcher for Amnesty International, said of Wu. “The authorities wanted to deal a heavy blow to scare off other activists.”

In its verdict, which was posted online, the Tianjin No 2 Intermediate People’s Court said that Wu had attempted to overthrow China’s socialist system by conspiring with “illegal religious practitioners”, “professional petitioners” and lawyers.

“Wu Gan has been proactive in carrying out criminal acts – the situation was severe, the damage [he caused] to society was serious,” it said. “He should be punished with a heavy sentence according to the law.”

“[They] use ‘defending rights’ and ‘performance arts’ as a disguise … to defame state institutions and attack the national system set by the constitution,” it said.

Before his trial in August, Wu said in a statement released by his lawyer that he expected a heavy punishment because he had refused to accept a government-designated lawyer or speak to state media.

In Xie’s verdict, the judge at Changsha Intermediate People’s Court said the 45-year-old lawyer, who represented Chinese villagers as they sought to sue local governments for seizing their land, was shown leniency as he had pleaded guilty and expressed regret.

His case drew international attention after his lawyer, Chen Jiangang, said Xie had been beaten and deprived of sleep, water and medical care while in detention.

At his trial in May, however, Xie denied being tortured and pleaded guilty to the subversion charges. His wife and supporters said he had been coerced into discrediting himself.

In a video released by the court on Tuesday, Xie again denied he had been tortured and apologised for misleading the public.

“I am grateful to the judiciary for their lenient treatment. I will in the future be a citizen who follows discipline and obeys the law,” he said while holding a handwritten script.

“If you cooperate with the government, then you will be given a more lenient sentence and a so called more open trial,” Poon said. “It is an alarming trend, because pushing people to confess in front of a camera is not how the rule of law should be practised.”

Timing the announcement to coincide with the Christmas holiday was also not a coincidence, Poon said.

“Carrying out unfair trials and politicised sentencing of human rights defenders at the very time when diplomats, journalists, international observers and the general public are less likely to be able to respond reeks of a cynical political calculation,” he said.

Liu Xiaobo, one of China’s best known human rights campaigners and a Nobel Peace Prize winner, who died in custody earlier this year, was similarly sentenced during the Christmas holidays, he said.