Although it has no legal authority to detain suspects, critics say, they frequently do so and sometimes even resort to "enhanced interrogation." They confiscate merchandise and impose arbitrary fines, leading critics to suspect corruption.
They are also known to collude with property developers to evict people.
Human rights groups have called on the Chinese government to clip the chengguan's powers and investigate its violent acts.
"The chengguan are not protecting the safety of Chinese citizens, they're actively undermining it," said Sophie Richardson, China director at Human Rights Watch. "The Chinese government can signal that it's serious about meaningful rule of law by ending chengguan abuses and impunity."
The Chinese leadership recognizes the risks posed by growing social discontent, but seems unable to find fundamental solutions.
It fears that political liberalization might lead to massive "dongluan" (chaos).
Such fear drives the Chinese leaders to seemingly contradictory policies and behavior.
Instead of addressing legitimate complaints, officials tend to resort to force and intimidation. Many cities have set up elite police squads to deal with riots and "terrorism."
They say they encourage "whistleblowers" to expose abuses, but when they aim at abusive officials, they get muzzled.
Li Chengpeng, one of China's most influential bloggers, recently had his Weibo account suspended after he posted a pointed essay about Ji Zhongxing's case. Ji, 34, had long been silenced by a system that tolerates little dissent, he said.
The Shandong native has been paralyzed since 2005, when he was allegedly beaten up by several "chengguan" officers while working as an unlicensed motorcycle driver in southern Guangdong province. He was suing for damages, asking for over 334,000 yuan (about US$53,000) but to no avail.
"I am now festering away, paralyzed and over 100,000 yuan in debt," he posted on his blog that has since been deleted. "The only thing that is keeping me going is the thought of seeking justice."
In desperation, Ji brought his struggle for justice to Beijing, adding his voice to the chorus of discontent.
Chinese political scientist Li Fan says Chinese leaders can ignore this rising chorus at their own peril.
"The airport bombing shows that when people are hopeless they will resort to more violence," he explained. "It's dangerous because next time someone will think, if no one listens, take even more radical steps, then your voice can reach the top and your case can be solved."
Li, author of the book "The Rise of Civil Rights Movement in Contemporary China," believes the old petition system has very limited role.
"The Chinese government should give people more space, to be able to speak out and participate in local affairs. It's a good way to defuse the anger of the people," said the Beijing-based political scientist. "Otherwise there will just be more and more protests."