Ten people have been sentenced to prison for illegally detaining petitioners who had travelled to Beijing, to appeal to the government, state media reported, in a possible sign the government is trying to rein in abuses.
The group rounded up 11 petitioners from Henan province in April 2012, Xinhua news agency said, and illegally detained them in a courtyard in Beijing for several days.
Tuesday's court ruling is an apparent blow on attempts by local governments to cover up abuses.
The defendants, who were also from Henan, received terms of between six months and two years.
The court in Beijing said they had violated the petitioners' rights. The 10 defendants were also ordered to pay compensation to those they detained, the Xinhua report said.
Illegal detention of petitioners is believed to be common, but is, like all legal and public order issues in China, a matter of great sensitivity.
Such petitioners are frequently intercepted by local government agents and detained illegally in hostels known as "black jails".
'Black jails exist'
Al Jazeera's Marga Ortigas, reporting from Hong Kong, said such sentences "have never been acknowledged or publicised".
"With this sentence made public, the central government is clearly sending out a signal or at least acknowledging that 'black jail's' exist and that local authorities who have been abusing their powers will no longer be tolerated," Ortigas said.
The government has recently begun acknowledging the existence of such places as part of modest attempts to stamp out such abuses of power.
The petitioning system dates back to ancient times when Chinese emperors were obligated to hear complaints brought from commoners in the provinces.
In recent years, it has been employed to skirt violence, threats and bureaucratic hurdles put in place to block redress over corruption, illegal land seizures, unjust discrimination and other abuses at the local level.
Black jails have also been used in the past to detain political and religious dissident.
"This certainly does not go to the root of the problem, because what is lacking is democracy and checks and balances at the local level, so that the local government understand that they have to observe the law and respect the rights of the people," Prof. Joseph Cheng, of the City University of Hong Kong, told Al Jazeera.