A court in China has sentenced prominent rights lawyer Wang Quanzhang to four and a half years in jail for "subverting state power", in a verdict that sparked criticism from human rights activists.

Wang, who had taken on cases deemed sensitive by authorities in Beijing, including allegations of police abuse and defending members of the banned Falun Gong spiritual movement, went missing in 2015, amid a sweeping crackdown on rights activists and lawyers.

In a short statement on its website on Monday, the Tianjin Second Intermediate People's Court in the northern port city of Tianjin released a verdict, saying that Yang had been found guilty.

Wang was "found guilty of subverting state power, sentenced to four years and six months in prison, and deprived of political rights for five years," the court said in its statement.

It is not possible to contact Wang for comment.

The 42-year-old had been the last of more than 200 lawyers and activists arrested in the crackdown to be tried or released. The event is dubbed "709" because the arrests started on July 9, 2015.

After Wang's hearing in late December, the United Nations called for Chinese authorities to "ensure his due process rights are respected" and said that there were "serious human rights concerns" about the way his case had been handled.

The verdict makes a "mockery" of Chinese President Xi Jinping's claims to champion the rule of law, Yaqiu Wang, a Hong Kong-based Human Rights Watch (HRW) researcher said in a statement.

China's criminal law requires the time suspects spend in detention prior to being sentenced be deducted from jail time, meaning Wang should be released earlier than his sentenced time period, she added.

During his court appearance, Wang fired his state-appointed lawyer, according to Li Wenzu, his wife, who was unable to attend due to being barred from leaving her Beijing home by Chinese police and state security agents.

It is unclear whether Wang defended himself during the trial or whether he will appeal the sentence.

Li has vocally championed her husband's case in the three years since he went missing, staging a 100km march from Beijing to Tianjin, shaving her head to protest his treatment and filing almost weekly petitions to the Supreme People's Court.

Wang's case has been shrouded in secrecy and uncertainty, as authorities have released little information about his well-being and have denied access to Li and the seven lawyers she has appointed to defend him.

Yu Wensheng had been Wang's defence lawyer before he was stripped of his license and then arrested in January. He is now being investigated for "inciting subversion".

Police turned Western diplomats and foreign journalists away from the court on the day of Wang's hearing and arrested activists Yang Chunlin, who had travelled to Tianjin to support Wang.

An indictment document from 2017 said that Wang had "for a long time been influenced by infiltrating anti-China forces" and had been trained by overseas groups and accepted their funding.

China routinely rejects foreign criticism of its human rights record, saying all Chinese are treated equally in accordance with the law and that foreign countries have no right to interfere.