Community patrols talks with each other on a street in Beijing, March 8, 2011. [Photo/IC]

Clues provided by residents in Chaoyao have also proved valuable in helping police crack cases about illegal constructions, fire hazards and unlicensed taxis, so on so forth.

Who are they?

"I believe BJCYQZ refers to ordinary people who believe in justice, abide by the law and have the courage to fight against crime," said Li.

Sun Zongfen, 73, and people like her conduct regular patrols of their community, which features new comers because it's close to a hospital and a flea market frequented by foreigners.

"I came across a stranger entering our unit carrying something unusual, who failed to tell me which floor he lived, so I followed him upstairs and found out that he was a new tenant," said Sun, "If he shows more suspicious behavior, I will report it to the police."

"We have a hotline with the director of our local police station, the officers of which will arrive within 10 minutes after they receive our call," said Yu Xiaohui, a community patrol who has lived in her community for 32 years. "We know everyone in our apartment building."

No crimes have taken place in Yu's community in 12 years even though the community has only two police officers.