Chinese authorities say they have arrested more than 10,000 suspects and smashed more than 600 gangs during a four-month crackdown on Internet crimes, according to news reports.
At the same time, Beijing police are threatening to punish any online "political rumor" or "attack" on Communist Party leaders, the system or the country, raising fears of tighter controls on speech on the country's 538 million Internet users.
The Ministry of Public Security said "major crimes uncovered" during the nationwide operation since May include pornographic information, gun trading, wiretapping devices, counterfeiting, as well as illegally collecting and selling citizens' personal information, the official Xinhua News Agency writes.
The cyber-police have also deleted 3.2 million messages deemed "harmful," closed hundreds of Internet cafes and punished 30 service providers for granting access to unlicensed sites, the BBC says.
Additionally, 62 websites and online forums were ordered to remove "inappropriate content."
In southern China, police reported detaining "a gang of hackers" believed responsible for attacks on 185 government websites, the state-run China Daily newspaper says.
The warning from Beijing's Public Security Bureau about Internet comments came Tuesday during a meeting about protecting minors online, the Global Times reports.
In May, a BBC article asked, "Will China's Great Firewall backfire?"
China's crackdown comes as the U.S. Congress is considering new cybersecurity legislation.
The Senate voted today to begin debating and amending the Cybersecurity Act of 2012, which is intended to bolster cyber-defenses against attacks on communications systems and infrastructure.
The measure "calls for the Department of Homeland Security (DHS) to assess risks and vulnerabilities of computer systems running at critical infrastructure sites such as power companies and electricity and water utilities and to work with the operators to develop security standards that they would be required to meet," Cnet wrote when the legislation was introduced in February.
The Electronic Frontier Foundation says the Cybersecurity Act "poses serious threats to online rights."
The House approved a similar bill in April -- the Cyber Intelligence Sharing and Protection Act -- despite a threatened White House veto. The measure encourages but does not require companies and the federal government to share information collected on the Internet to prevent against online attacks.