Migrant workers in the southern Chinese city of Zengcheng have been encouraged to inform on people involved in this month’s riots, in return for a promise of much sought-after residency rights.

A police notice published in the Zengcheng Daily newspaper at the weekend offered rewards to individuals who provided information on suspected rioters, including up to Rmb10,000 ($1,545) in cash, a “good citizen” award, and for migrant workers, a local household registration. The offer of residency rights is particularly attractive because China’s outdated household registration – or hukou – system only grants access to education, healthcare and other social benefits to local families.

It has been criticised for depriving an estimated 153m migrant workers of basic rights and fuelling social discord.