For a government that keeps a tight grip on information, this was a week when it lost control of the narrative.

In the diplomatic standoff over blind activist Chen Guangcheng, technology and growing social-media savvy helped spread, drive and at times even muddy a story rife with unexpected twists.

The round-the-clock use of Twitter and other social media by Chinese activists kept foreign journalists and human rights groups overseas apprised of developments in real time, even as authorities tried to isolate Chen and his supporters.

U.S. diplomats believe they have secured a tentative deal that would allow Chen to leave for the United States. Meanwhile here in China, the role of social media in highlighting his case, and in detailing the harsh treatment meted out to his friends and supporters, seems for many to mark a seminal moment in the Communist government’s decades-long history of repressing dissent and stifling information.

The Communist Party controls most major newspapers and virtually all television in China. But the advent of Twitter-like microblogging sites called Weibo in recent years has given urban Internet users an alternative to state-controlled media.

And it is through that social media, as well as cellphones and text messages, that much of the information came through about Chen’s whereabouts and wishes, and about the fate of those who helped him escape. Many activists also relied notably on Twitter itself, which is blocked in China but can be accessed by exploiting holes in the “Great Firewall” that censors the Chinese Internet.

When Chen was driven from the U.S. Embassy to a nearby hospital and made a telephone call from the van to The Washington Post, the news broke first on Twitter. It was Chen’s friend Zeng Jinyan, another activist, who first informed the world via Twitter that Chen had been left alone by U.S. officials at the hospital and was afraid. Zeng also tweeted that thugs in Shandong province, where Chen is from, had threatened to beat his wife to death, and that Chen wanted to leave China for the United States.

And the next day, Zeng broadcast on Twitter that she was being followed by plainclothes police and had been placed under house arrest. She even warned journalists not to try calling her.

A particularly dramatic moment came Thursday when Chen — isolated in his Beijing hospital room but with a cellphone at hand — called into a U.S. House of Representatives hearing on the handling of his case and expressed concern for his family left behind in Shandong.

‘Total sea change’

Twitter and Weibo similarly became essential for journalists and overseas human rights activists who used it to pass along phone numbers and links to photographs of Chen in the hospital and of plainclothes officers keeping reporters and diplomats outside. When Chen’s allies or supporters were detained, and when or if they resurfaced from police detention, word spread first on Twitter, often followed by text messages.

“It is almost mind-blowing to see his friends posting on Twitter conversations with him, things like who picked him up in Beijing and where,” said Kenneth Lieberthal, a China expert with the Brookings Institution in Washington. “It’s a total sea change from how this may have been handled decades ago.”

The Chen episode follows closely another blockbuster in China — the fall from power of the once high-flying Chongqing Party boss Bo Xilai. That political story became the most watched and most reported in a generation.

With precious few official announcements about Bo beyond the early, terse statement that he was being investigated for “serious discipline violations” while his wife is a murder suspect, the Bo family scandal has mostly unfolded online.

Stories posted and reposted online have looked into the Bo family’s financial holdings, the dealings of extended family members, and even the overseas university partying habits of Bo’s son, Bo Guagua.

In both the Chen case and the Bo Xilai story, the official state-run media has tried to squeeze the information flow to a trickle. In both cases, their attempts have largely failed.

“It really illustrates the challenge that social media poses for systems that rely on an extremely tight control of information,” said Nicholas Bequelin, senior Asia researcher for Human Rights Watch and based in Hong Kong. “The erosion of information control is an enormous challenge for the party.”

July train crash

Even before Bo and Chen, an event on July 23 pointed to how pivotal microblogs had become. When two high-speed trains collided in Wenzhou, in Zhejiang province, killing 40, people immediately used their cellphones and tablets to take and post photos of the wreckage and the rescue efforts, long before the state-run media even acknowledged the crash.

When China’s censors ordered the state-run media not to report on the incident or the investigation, except for official pronouncements, most news about the causes and the ensuing investigation came from Weibo.

China has stepped up efforts to rein in the freewheeling Weibo culture, including implementing new rules requiring users to register with their real names and identity card numbers, so they can be more easily traced. Authorities have also clamped down on Weibo “rumor-mongering,” closing down at least 16 Web sites and arresting several people. The comment functions of the two most popular microblogging sites were temporarily disabled.

But Chinese “netizens” are constantly outpacing the censors.

Shortly after word of Chen’s escape emerged, for instance, authorities scrambled to limit what was known about him online, banning from Weibo search engines Chen’s name, his initials, “Blind Man,” and even code names such as “C-Guang-C.” But the censors went further, banning Weibo searches for his home city, Linyi, and his village, Dongshigu. Also banned were the movie titles that were being used as code words: “The Shawshank Redemption” and “The Great Escape.”

Chinese media finally broke its silence Friday, and four Beijing newspapers ran coordinated editorials attacking Chen and U.S. Ambassador Gary Locke for assisting him. But netizens again displayed their power.

Outraged readers bombarded the comment sections of the Beijing Daily, defending Locke and Chen. Soon, even “Beijing Daily” joined the list of banned search terms.

One of the newspapers, the Beijing News, even ran what appeared to be a contrite apology for its own editorial the next day.

In a Friday editorial, the paper wrote that “1.3 billion Chinese people cannot be fooled so easily.” It was referring to Chen and his supporters. But it may just as easily have been referring to the Communist Party’s propaganda machine.

Staff writer William Wan in Washington contributed to this report.