China has at least 31 journalists behind bars, making it the world's leading jailer of reporters for the eighth year in a row, according to a US-based group's survey.
About three-quarters were convicted under vague charges of subversion or revealing state secrets, and more than half were Internet journalists, said a statement on the annual survey by the New York-based Committee to Protect Journalists or CPJ.
"China is challenging the notion that the Internet is impossible to control or censor, and if it succeeds there will be far-ranging implications, not only for the medium but for press freedom all over the world," CPJ Executive Director Joel Simon was quoted as saying in the statement released on Thursday.
China encourages Internet use for business and education but tightly controls Web content, censoring anything it considers critical of the Communist Party, or a threat to it.
Blogs are often shut down, and those who post articles promoting Western-style democracy and freedom are routinely detained and jailed under subversion charges.
Shi Tao, a former journalist for the Dangdai Shangbao or Contemporary Business Newspaper in the central province of Hunan, was sentenced last year to 10 years on charges of leaking state secrets.
Shi, 37, was alleged to have e-mailed the contents of a secret official memo about media restrictions to the US-based Democracy Forum website.
Journalism activists criticized U.S. Internet company Yahoo Inc after it emerged that it had given prosecutors e-mail from Shi's account.
Li Yuanlong, a reporter for the Bijie Daily newspaper in the southern city of Bijie, was detained in September 2005 after posting essays on foreign Web sites.
His essays, written under the pen name Ye Lang or "Night Wolf," included "On Becoming an American in Spirit" and "The Banal Nature of Life and the Lamentable Nature of Death."
They were published on sites banned in China, including Boxun News, the Falun Gong-affiliated Epoch Times, ChinaEWeekly, and New Century Net, according to earlier reports.
In July, Li was convicted of inciting subversion and sentenced to two years.
Last week, a Beijing court took five minutes to reject an appeal, made by New York Times researcher Zhao Yan against his three-year prison sentence.
Zhao had been convicted of fraud, but press advocacy groups saw his case as a political vendetta for his pre-Times career as a crusading investigative reporter -- and as a warning to Chinese reporters.
"What kind of judge are you?" Zhao asked the judge, according to the Times, which cited a courtroom witness it did not name.
"Is this how you use the power the country gave you?" The CPJ survey found the total number of journalists jailed worldwide had risen to 134 as of December 1 -- nine more than a year earlier.
The number of jailed journalists in China had fallen by one from last year, the CPJ figures showed, following the release in September of writer and pro-democracy activist Zhu Yufu.
Reporters Without Borders maintains its own tally of Chinese reporters and cyber-dissidents behind bars, with a count of 32 as of January this year.
The Paris-based group lists 19 people, including five Tibetan monks who were arrested last year for allegedly starting an underground newsletter, who are not named on CPJ's list. The two combined total 50 journalists.