The Xinhua news agency's denunciation of Internet "rumor mongering" came after a senior official last week urged Sina Corp and other Chinese companies do more to staunch harmful hearsay among the 200 million or more Chinese who use Twitter-like microblogs to spread information with lightning speed.
China's Internet, with more registered users than any other nation, is a lively forum for public opinion, said Xinhua.
"However, the rapid advance of this flood has also brought 'mud and sand' -- the spread of rumors -- and to nurture a healthy Internet, we must thoroughly eradicate the soil in which rumors grow," it added.
"Concocting rumors is itself a social malady, and the spread of rumors across the Internet presents a massive social threat," it said, noting the capacity of blogs and microblogs to spark the "explosive" proliferation of falsehoods.
A Xinhua comment does not amount to a policy directive, but this one and other recent signals suggest tighter censorship, whether formal or informal, is on policy-makers' minds.
"Fundamentally eradicating the soil in which rumors sprout and spread will demand stronger Internet administration from the responsible agencies, raising the intensity of attacks on rumors," said the Chinese-language Xinhua commentary.
The feverish growth and growing influence of microblogs appear to have unsettled officials, who have complained that such sites can spread baseless rumors unchecked, sowing panic and distrust of government.
The number of Chinese people using microblog sites reached 195 million by the end of June, an increase of 209 percent on the number at the end of 2010, according to the China Internet Network Information Center. But Sina this month reported that its microblogging "Weibo" site, which dominates the scene, alone had grown to 200 million registered accounts.
These microblogs allow people to shoot out short bursts of opinion, presenting a quandary for censors. They fear an uproar if they shut the popular sites, but struggle to keep ahead of the rapid-fire messages that can spread news and opinion the government, wary of any social unrest, would like to contain.
China's state-run television news recently denounced the spread of unfounded rumors on microblogs, called "Weibo" in Chinese, and demanded more be done to staunch accusations of official foul play, corruption and misdeeds that officials have said can spread in spite of no supporting evidence.
Many users of Sina's site (weibo.com) leapt on the Xinhua comment as evidence that tighter censorship is coming.
"If this was really about quashing rumors, Internet users would surely welcome that, but I fear that this is not about mere rumors," wrote one user.
"It's more about waving this banner as a pretext to cleanse so-called rumors and ban the people from telling the truth."
China's microbloggers showed their potency in a string of recent official scandals, particularly the online uproar in the wake of a high-speed bullet train crash in July that killed 40 people. Microbloggers led the charge in challenging rail officials' evasive accounts of the disaster.
Last week, Sina sent out messages that microblog users had their accounts frozen for a month for spreading false rumors: one saying the Red Cross Society of China profiteered from donated blood; another that the killer of a young woman escaped punishment because of family political connections.
The Communist Party secretary of Beijing, Liu Qi, also weighed in. During a visit to Sina.com's offices in the national capital, Liu both praised and chided the Weibo site.
"Internet sites must actively explore strengthening administration and resolutely blocking the spread of false and harmful information," he said, according to a report in the Beijing Daily.
For critics, such words augur stricter censorship of the Internet, especially news and comment unwelcome to wary party officials, irrespective of whether it is true or false. China heavily filters the Internet, and blocks popular foreign sites such as Facebook, YouTube and Twitter.
Sina and other Chinese microblog operators already deploy technicians and software to monitor content, and block and remove comment deemed unacceptable, especially about protests, official scandals and party leaders.
The Xinhua commentary said police should mete out more punishment to people found culpable of spreading falsehoods.
"To staunch the spread of rumors, have the central leaders face up to their history, have Xinhua end bogus news, have the National Bureau of Statistics end fake data," said one Sina microblog user, denouncing the Xinhua commentary.
"The most effective way to eradicate rumors is openness and transparency," wrote another.
(Reporting by Chris Buckley; Editing by Ken Wills and Sanjeev Miglani)