A southern Chinese city is offering cash rewards for information about "illegal religious groups" as the ruling Communist Party continues to tighten its grip over faith communities.

A notice posted on the official website of the Guangzhou Department of Ethnic and Religious Affairs said up to 10,000 yuan ($15,000) would be paid for verified information and assistance in hunting down key members and leaders of illegal foreign religious groups and revealing their structures.

The department said smaller rewards would be offered for reports about religious venues set up without permission and behavior encouraging "religious extremism."

Under President Xi Jinping, the officially atheistic ruling party has sought to eliminate all religious expression not under its direct control, especially that by Uighurs, Kazakhs and other Muslim ethnic minority groups.