A bombing at Beijing airport by a wheelchair-bound man who complained for years about police brutality spotlights how frustration over low-level abuses in China can flare up to trouble the authorities, analysts say.
Ji Zhongxing, a 34-year-old former motorcycle driver, had lost hope of obtaining redress for a 2005 beating that left him paralysed, reports said.
In a desperate attempt to draw attention to his plight, he built a home-made bomb and set it off in the airport arrivals area after handing out leaflets about his case.
His story echoes countless other episodes of low-level officials dealing violently with ordinary citizens and then denying responsibility -- such as a confrontation last week that left a watermelon vendor in the central province of Hunan dead.
China's new leaders took office in March pledging cleaner government that better serves the people, acknowledging that discontent with authorities poses a threat.
Last month Chen Zhuizong blew up a bus in the southeastern city of Xiamen, killing himself and nearly 50 other people, after writing online he had appealed unsuccessfully to local police 56 times over social security benefits.
But the surprise, analysts said, was that similar incidents did not happen more often.
"Obviously (the airport bombing) is quite high-profile because of where it took place, and that's attracted people's attention, but dissatisfaction with local government officials is very, very intense," said Kerry Brown, a Chinese politics professor at the University of Sydney.
"It's actually probably surprising that it's not actually a bigger number, if you think about how many people are angry."
Protests -- about anything from abuse to corruption to pollution -- top 180,000 a year in China, academics have estimated, even as the government devotes vast sums to "stability maintenance", with payments particularly going to the military.
But legal paths for Chinese to pursue justice are limited. The courts are subject to political influence and corruption, and a system meant to let citizens lodge complaints about authorities is ineffective, with petitioners routinely finding themselves detained.
Rejecting Ji's complaint of brutality, the government of the southern city of Dongguan said he had been in a road accident with local officials and denied any violence had occurred.
It said in a microblog post that Ji had submitted petitions and lost a court case for compensation, and that it had ultimately given him 100,000 yuan ($16,000) in financial aid.
Weibo users cast doubt on that version of events while expressing sympathy for Ji, who at the airport had warned people away before setting off his device, causing injury only to a police officer remonstrating with him and destroying his own left hand.
"Senior officials, please pay attention... disregarding people's experiences and needs -- if this continues the country will fall apart," lawyer Li Weimin posted.
"If the local government had no responsibility in this case, why were they willing to give him 100,000 yuan? If they had responsibility, why didn't they deal with it in accordance with the law?"
Local officials on the "front line" who carry out "the state's dirty work", such as collecting taxes and enforcing the one-child policy, make matters worse by routinely resorting to violence and cover-ups, Brown said.
Particularly disliked are "chengguan", tasked with enforcing non-criminal regulations in cities. A Human Rights Watch spokeswoman last year said they were "synonymous for many Chinese citizens with physical violence, illegal detention and theft".
Last week 56-year-old watermelon seller Deng Zhengjia died in an encounter with chengguan in Hunan, stoking anger.
Media reports citing his wife said an officer smashed Deng's head with a metal measuring weight. The county government denied the claim and a news portal linked to it said Deng had suddenly fallen to the ground and died.
Conflict with local officials stretches back years and it is hard to know whether it has become more frequent or more commonly reported, said Joseph Cheng, a China politics expert at the City University of Hong Kong.
In a high-profile case in 2008, Yang Jia, 28 at the time, was the object of widespread sympathy after he fatally stabbed six Shanghai police in what he called revenge for a wrongful arrest. He was executed months later.
"This of course is not right, but at the same time these attitudes reflect the grievances on the part of the ordinary people," Cheng said.
He added that China's new leaders could make good on pledges to better address people's needs, and boost their own image, by creating a system to punish low-ranking officers.
But preventing further incidents would require higher-reaching reform, which Brown said was unlikely.
"Their default position at the moment is just containment rather than doing anything about root causes. That'll take something incredibly unpleasant happening in the future," he said.
"It's a horrible thing to think that."