China has banned the widespread practice of detaining petitioners seeking government redress, state media said Thursday, following the abolition four months ago of "re-education through labour".

Similar pledges have been made before, but detentions have continued nonetheless.

Chinese citizens unable to find redress from local officials often appeal to higher-level authorities, sometimes travelling cross-country to Beijing.

But they are routinely ignored by government offices, or thwarted by embarrassed by hometown officials and forced into informal "black jails" before being bundled home.

Government bodies must now "resolutely (avoid) blocking the people from normal petitioning by any means", said a circular issued by the ruling Communist Party's Central Committee and the State Council, China's cabinet, the official news agency Xinhua reported.

"The circular stresses that illegal or indirect confinement of petitioners is strictly prohibited," Xinhua said.

The document instructed officials instead to meet with petitioners and either funnel their complaints to the court system or explain why they were rejected.

Xinhua admitted that when petitioners presented grievances ranging from land acquisition to healthcare to environmental protection, "officials often prevent them from raising such cases with their superiors".

The move follows a decision by Beijing last November to end a decades-old system of "re-education through labour" camps, where petitioners and minor offenders could be sentenced for up to four years by a police panel, without appearing before a judge.

But detention of petitioners seem to have continued -- in February, the central province of Henan admitted shutting petitioners in "discipline centres".

Meanwhile, rights groups have warned that despite the closure of labour camps, arbitrary detention persists through "black jails", enforced disappearances and other methods.

Many labour camps were converted into drug rehabilitation centres that operated "virtually identically", the advocacy group Amnesty International said in December.