What started as a mildly annoying encounter on Oct. 18 between a porter and a man who claimed to be a senior official in Wanzhou, in central China, turned into a full-scale riot, fed by resentment among poorer residents.

ANZHOU, China, Dec. 24 - The encounter, at first, seemed purely pedestrian. A man carrying a bag passed a husband and wife on a sidewalk. The man's bag brushed the woman's pants leg, leaving a trace of mud. Words were exchanged. A scuffle ensued.

Easily forgettable, except that one of the men, Yu Jikui, was a lowly porter. The other, Hu Quanzong, boasted that he was a ranking government official. Mr. Hu beat Mr. Yu using the porter's own carrying stick, then threatened to have him killed.

For Wanzhou, a Yangtze River port city, the script was incendiary. Onlookers spread word that a senior official had abused a helpless porter. By nightfall, tens of thousands of people had swarmed Wanzhou's central square, where they tipped over government vehicles, pummeled policemen and set fire to city hall.

Minor street quarrel provokes mass riot. The Communist Party, obsessed with enforcing social stability, has few worse fears. Yet the Wanzhou uprising, which occurred on Oct. 18, is one of nearly a dozen such incidents in the past three months, many touched off by government corruption, police abuse and the inequality of the riches accruing to the powerful and well connected.

"People can see how corrupt the government is while they barely have enough to eat," said Mr. Yu, reflecting on the uprising that made him an instant proletarian hero - and later forced him into seclusion. "Our society has a short fuse, just waiting for a spark."

"May you live in interesting times." -- Ancient Chinese Curse