BEIJING -- Hundreds of people took to the streets of a city in China's southern Guangdong Province on Friday to protest a proposed uranium processing plant that would be the nation's largest when completed.
Participants said that as many as 1,000 residents "took a walk" through Jiangmen, a city less than 60 miles from Hong Kong, to express their opposition to the plant, which officials say could enrich enough nuclear fuel to provide roughly half of China's atomic energy needs by 2020.
Unsanctioned public gatherings are prohibited in China, but marchers said the police largely held back as the crowd moved through the city carrying banners that read "Yes to Children, No to Nukes" and "Fight Nukes or Die!"
Organized through social media and billed as an innocent stroll through the streets of Jiangmen, the demonstration was the latest example of urban Chinese willing to defy the authorities over environmental concerns. The government would not likely tolerate a similar gathering to demand political reform or an easing of news media restrictions.
Reached by phone, several residents said they were outraged to learn about the plant only last week when the government announced the project and then gave the public 10 days to submit comments. "They didn't even let us know about it until it was almost started," one man, Liang Naihe, said in an interview.
The authorities apparently worked hard to head off the protest by deleting posts on Sina Weibo, China's version of Twitter, but some participants said they learned about it through WeChat, an increasingly popular walkie-talkie-like app that is harder to censor.
A 26-year-old accountant who joined the protest said that most of the marchers were tech-savvy college graduates in their 20s and 30s, but that there was also a large number of factory workers who had been given time off by their supervisors so they could join. He said the protesters were planning to return to the streets on Sunday if the government refused to cancel the $6.5 billion project.
"Even though the government claims that this plant is harmless and 100 percent safe, we just don't trust them," said the accountant, who gave his name as Ah Ding. "We're already scared to drink the water. Maybe it will be O.K. for this generation, but what about the next?"
Local officials, seemingly startled by the size of the protest, responded by holding a news conference, where the mayor promised to extend the public comment period by another 10 days.
Critics said they were most bothered by the lack of transparency and their inability to play any role in determining where the plant would be located. The Jiangmen City Development and Reform Bureau has so far offered scant detail about the production process, how the spent nuclear fuel would be handled and where it would be stored.
"The main concerns are not about an accident but about leaks and safety," said Prentice Koo, a senior campaigner at Greenpeace in Hong Kong. "Right now the information provided to the public is not really enough to assess the risks."
Seeking to calm nerves, the local government posted a question-and-answer section on its Web site, although many of the answers were decidedly lacking in substance. One questioner asked about the potential dangers should the plant be bombed during a hypothetical war with the United States. The answer: "Given that it is a civilian nuclear facility, the plant is protected by international law and could not be attacked during wartime."
Many people were not convinced. Some, including Chen Guanming, took to Weibo to express their displeasure. Mr. Chen said that if there was no stopping the plant, he had just one request: "All municipal leaders and their families should live near the plant. Let them enjoy their great achievement at closest range, and then we won't have anything more to say."
Patrick Zuo and Yuan Chang contributed research.
This article originally appeared in The New York Times.