BEIJING: Ten people who detained citizens trying to lodge complaints against Chinese authorities have been sent to prison, state media said Tuesday, in a rare gesture towards upholding petitioners' rights.

Under China's ancient petitioning system, individuals can ask Beijing to investigate disputes such as land grabs and unpaid wages, but local governments regularly hire "interceptors" to physically prevent complaints being filed.

Bureaucrats face threats to their careers if too many complaints are made from their areas, and petitioners are regularly detained in secret facilities known as "black jails" to stop them doing so.

The defendants, all from Henan, held the petitioners -- from the same central province -- for up to six days in the capital in April last year before themselves being arrested, state-run news agency Xinhua said.

Wang Gaowei and nine accomplices "infringed the personal rights of the 11 petitioners, which constituted the crime of false imprisonment", it cited the court as saying. They were jailed for between six months and two years.

It was not yet clear whether the case represented a significant step towards guaranteeing petitioners' rights, said Hong Kong-based human rights researcher Joshua Rosenzweig.

"It remains to be seen whether this is the first in a series of cases like this, in which case we will look back at this as a significant step," he said.

"There are not only 10 people involved in the interception of petitioners."

Immense pressure on local politicians to "maintain stability" -- the official euphemism used to describe clamping down on dissent -- means that incentives to suppress petitioners remain.

"There is a climate in which the priority has been placed on maintaining stability at the local level... which is part of the reason why (local officials) are so anxious to take petitioners out of Beijing," Rosenzweig said.

The Beijing Youth Daily, which reported the case last year, cited petitioners as saying their interceptors had beaten them and wore badges identifying them with the Henan government.

Despite years of calls for China to shut down its "black jails", including from the country's media, rights groups continue to report frequent cases of petitioners being illegally detained and physically assaulted.