BEIJING (AFP) - A Chinese court on Tuesday (Aug 2) handed a rights activist a three year suspended jail sentence for organising street demonstrations, state media said, the latest conviction in a sweeping crackdown on dissent.

Zhai Yanmin was convicted of "subverting state power" for acts including waving banners and shouting slogans in four protests since 2014, the official Xinhua news agency cited a court in the northern city of Tianjin as saying.

Zhai was held more than a year ago in a sweeping crackdown which saw more than 200 lawyers who had taken on civil rights cases considered sensitive by China's ruling Communist Party and activists held for questioning.

About a dozen remain under arrest on "state subversion" charges. Zhai, who was unemployed, was the first of the group to be convicted, with further trials expected this week.

China's President Xi Jinping has overseen a tightening of controls on civil society since assuming power in 2012, closing avenues for legal activism which emerged in recent years.

The court ruled that "though illegal and provocative assemblies in public places" Zhai had "attacked the national legal system", Xinhua said.

Together with several human rights lawyers he had "plotted to overthrow state power, adopting a systematic style of government-overthrowing thought", it added.

Evidence presented at the trial, which apparently lasted only a few hours, included banners, books and "audio and video recordings", Xinhua said, without giving their provenance.

Zhai's wife Li Ermin was put under house arrest early Tuesday and could not attend the trial, a close friend told AFP.

Police surrounded the courthouse in Tianjin for the verdict, turning away foreign media hoping to report on the case.

In an unusual move, four Hong Kong media outlets were permitted inside, the South China Morning Post (SCMP) newspaper said.

The sentence, relatively lenient by the standards of Chinese dissident prosecutions, came after Zhai "admitted" to prosecutors' accusations in court, Xinhua said.

He also provided testimony implicating prominent human rights lawyers including Zhou Shifeng and Li Heping in state subversion, Xinhua said.

Zhou - the director of the Fengrui law firm at the centre of the crackdown last July - will also go on trial on subversion charges this week, the SCMP said.

Another prominent Fengrui attorney, Wang Yu, who was detained over a year ago, has been released on bail, a Hong Kong TV channel said Monday, as it showed her praising her jailers.

It was not clear whether Zhai had been released following the verdict. Authorities in Tianjin could not be reached for comment.