Google shut its mainland Chinese-language portal and began rerouting searches to its Hong Kong site, prompting concerns over its future business in China.
China lost little time in warning Google that its rejection of self-censorship was a breach of an agreement struck when the search engine company first started operating in the country.
Chinese foreign ministry spokesman Qin Gang would not say directly whether his government considered Google's new Internet arrangements legal, merely noting that government departments would handle it in accordance with the law.
"The Google incident is the individual act of a commercial company. I don't see that it would have any impact on China-U.S. relations, unless some people want to politicise it," Mr Qin told a regular news conference.
The decision comes amid heightened tensions between Beijing and Washington over a range of issues, from Internet freedom to the yuan exchange rate, economic sanctions on Iran and US weapons sales to Taiwan.
"Google has violated the written promise it made on entering the Chinese market," said an unnamed official from China's State Council Information Office, which helps oversee Internet rules, according to the Xinhua news agency.
"It is totally wrong in halting (censorship) filtering of its search provider," said the official. "We firmly oppose politicising commercial issues, and express our dissatisfaction and anger at Google Inc's unreasonable accusations and practices," said the official.
Google said in January that it would no longer censor its China-based Google.cn search portal and said it was also alarmed by hacking attacks from within China.
"It was not unexpected. How do you square the circle in a situation where your business globally depends on the free flow of information and one (side) restricts that?" Joerg Wuttke, president of the European Union Chamber of Commerce in China, said of Google's retreat.
Google acted on that threat, throwing the burden on Beijing to apply its own censorship filters to keep Chinese users from seeing banned images and words when rerouted to the company's Hong Kong site, google.com.hk.
Google said it intends to continue research and development in China, and keep sales staff there. But the company is likely to be closely watched by officials, possibly emboldened after months of friction with Washington.
"I don't think it's sustainable for Google to conduct rerouting of traffic," said Mr Edward Yu, chief executive of Analysys International, a Beijing-based research firm specialising in technology issues.
"The thing that makes the government unhappy is this kind of gesture. That Google will not follow (the rules), and that gesture will anger the government so they may set up barriers against Google."
Analysts said it was possible Google's plans for other services in China, such as its Android smartphone software, could be jeopardised by its move.
"Ordinary (Chinese) Internet users won't be much affected, because the only difference they'll see is that the burden of censorship has shifted from Google to the government," said Wang Junxiu, a Beijing-based Internet entrepreneur who has campaigned against online controls.
"But Google's business may take a hit. Advertising may fall, and (Chinese) companies that have invested in joining up with Google innovations and content will be hurt," said Wang.
An impasse seems likely after Google challenged China's ruling Communist Party, is wary of any political challenges in the world's third biggest economy.
China gave no ground on the censorship issue in its dealings with Google, the company's Chief Legal Officer David Drummond wrote in a blog post yesterday.
But he also wrote that "the Chinese government has been crystal clear throughout our discussions that self-censorship is a non-negotiable legal requirement."
Before Google made the move, users of Google.cn saw a warning that content banned by the government could not be viewed whenever they made a search.
Searches on the Hong Kong website from mainland broadband lines for sensitive news and discussion about jailed dissidents and banned organisations gave links to sites that google.cn previously did not.
However, these pages could not be opened.
Google.com can still be accessed from China.
While Google is the world's top search engine, it held only an estimated 30 percent share of China's search market in 2009, compared with home-grown rival Baidu Inc's 60 percent. Google's decision on Monday, therefore, won't have an immediate impact on earnings, analysts say.
China requires Internet operators inside the country to block words and images Beijing deems unacceptable. Google.cn used such a filter.
Internationally popular Websites Facebook, Twitter and YouTube are blocked in China, which also uses its own filtering "firewall" to block Internet users from overseas content banned by authorities.
Google said it was "entirely legal" for it to re-route traffic to an uncensored Hong Kong site, which uses simplified Chinese characters and is specifically designed for users in mainland China.
A former British colony, Hong Kong is a special administrative region of China and enjoys more freedom, including an uncensored Internet, than mainland China.
But Google acknowledged that the Chinese government could at any time block access to the services, which include Google search, news and images.
Reuters