Widening income gaps, corrupt local administrations and policies that seem to favor the well-connected few over the disadvantaged many are fueling spasms of violence that spring up in cities across China.

In the most recent case, more than 180 people died in ethnic violence that convulsed a Muslim area of western China last week. The spark for the unrest in Xinjiang was a brawl between majority Han Chinese and Muslim Uighur factory workers 1,800 miles away.

Weeks earlier, tens of thousands of people swarmed into the streets of a city in the country's heartland, overturning police cars and torching a hotel. The trigger for those riots, which left hundreds injured in Shishou, was the supposed suicide of a hotel chef.

Though the events that precipitated the two riots were strikingly different, the underlying forces behind them were in many ways the same. In neither instance did people believe accounts from the government and police, and their disbelief soon tapped into long-standing grievances — Uighur unemployment in Xinjiang and corrupt, mafia-like government in Shishou.

Tens of thousands of what the government calls "sudden mass incidents" rock China every year, presumably soaring in number since Beijing stopped releasing the statistic publicly in 2005, when there were 87,000 of them. While loss of life is rarely on the scale of the Xinjiang riot, protesters often vent their rage on public property, burning government offices and cars.

All told, the violence underscores how unfair China seems to many Chinese, rife with inequities that frequently cause unrest to bubble up. Social justice, a phrase banned by Internet censors earlier this decade, is now in vogue as the communist leadership realizes leaving the tensions unacknowledged risks its credibility.

Beneath the friction is China's rapid transformation into a highly competitive society. In the headlong rush from a poor, centrally planned and largely rural economy into the world-beating manufacturing and trading giant the country now is, many Chinese have lost the secure lifetime jobs and social safety nets they enjoyed a generation ago.

As standards of living have risen, so have aspirations — and frustrations when outside factors like kickbacks and nepotism further unlevel the playing field.

Over the past decade, the distribution of wealth has grown increasingly uneven. The U.N. Development Program puts China on a par with Mexico, a jarring change for a society that preached egalitarianism as recently as the 1970s.

After Xinjiang's communal eruption last week, in which Uighurs attacked Han Chinese and ransacked their shops and then Han groups retaliated, government officials said much of the violence was perpetrated by people from southern Xinjiang — a euphemism for the Uighur migrants who flock to the regional capital of Urumqi looking for work and often take low-paying jobs as fruit peddlers.

Insecurity is not confined to the less privileged. A fledgling middle class, worried over their futures, is also mounting protests.

A week before the Xinjiang riot, the hottest topic on the Internet — the most freewheeling public forum in China — was outrage over a top-scorer in the ultra-competitive college entrance exam.

The 17-year-old Han Chinese student's family falsely listed him as a minority, entitling him to 20 extra points and giving him a boost in landing places in top schools. The subterfuge, discovered by education officials, cut across notions of fairness in a society that for hundreds of years has seen standardized exams as a channel for merit-based advancement.

Fairness is more complicated when different ethnic groups are involved. Han Chinese tend to view ethnic minorities as privileged groups, generally exempt from the disliked one-child family planning limits and helped by reserved spots for government jobs and in universities.

Meanwhile, ethnic minorities see themselves as underprivileged, many of them poorer than the Han Chinese and with lesser education and language skills that make it harder to compete. It's worse for the Tibetans and the Uighurs, who see the Han as elbowing into what they regard as their homelands.

Government rhetoric does not ease the antipathy.

It immediately branded last year's uprising in Tibetan areas and this month's riot in Xinjiang as the work of terrorists, separatists and malign foreign forces, suggesting a plot to carve up China. Such language obscures these groups' grievances over government policies and feeds stereotypes among some Chinese that the Uighurs were ungrateful for the state's largesse.

The approach is unlike Beijing's treatment of unrest elsewhere in China, in which officials express sympathy and then often funnel cash payments to quiet the disgruntled unemployed laborers, dispossessed farmers and others at the center of local protests.

The strategy is known as "spending money to buy stability." Over the past month, state media has begun to question the tactic, running articles adding a modifier to the phrase: "spending money to buy temporary stability."

Charles Hutzler is The Associated Press bureau chief in Beijing and has covered China for more than a decade.