The accounts, posted on Sina Weibo, a Twitter-like service, were later deleted by the company’s in-house censors, but many postings were saved and reposted on overseas Web sites like Ministry of Tofu and China Digital Times whose servers cannot be reached by Chinese censors.

Even if a contretemps was defused, the specter of middle-class citizens fearlessly standing up to their otherwise omnipotent leaders is a scenario that fills Communist Party officials with dread. Xiao Qiang, director of the China Internet Project at the University of California, Berkeley, said the incident reveals the accumulated anger that many ordinary Chinese feel toward their government. “There was no serious injustice here, yet it did not take much for them to stand up and protest,” he said. “It’s the kind of thing that is very worrying to Chinese leaders because it could happen anywhere, at any time.”

In several recent clashes with the government, protesters have appeared to win. This month, thousands took to the streets of Shifang, a city in Sichuan Province, to oppose the construction of a $1.7 billion copper and molybdenum plant. Local authorities announced the suspension of the project after protesters attacked government offices and overturned police vehicles.

In August, more than 10,000 middle-class residents of Dalian, a port city in northeastern China, staged a peaceful street rally to demand the closing of a petrochemical plant that they said threatened public health. Officials pledged to move the factory, which makes paraxylene, a chemical used to manufacture plastic bottles and polyester clothing, but it remains in operation.

On Monday, dozens of people staged an impromptu sit-in on an upscale residential street in Beijing after their building’s management building cut water and power in a bid to extract more money from the tenants. The protest, which included a mix of Chinese and foreigners, worked. Utilities were restored by Monday evening.