SAN FRANCISCO — Google Inc. will stop censoring its search results in China and may pull out of the country completely after discovering that computer hackers had tricked human rights activists into opening their e-mail accounts to outsiders.

Yesterday's announcement is a major shift for Google, which has repeatedly said it will obey Chinese laws that require some political and social issues to be blocked from search results that are available in other countries.

Google disclosed in a blog post that it had detected a "highly sophisticated and targeted attack on our corporate infrastructure originating from China."

Further investigation revealed that "a primary goal of the attackers was accessing the Gmail accounts of Chinese human rights activists," said the post written by Google's chief legal officer, David Drummond.

Google did not specifically accuse the Chinese government. But the company added that it is "no longer willing to continue censoring our results" on its Chinese search engine, as the government requires. Google said the decision could force it to shut down its Chinese site and its offices in the country.

Danny O'Brien, international outreach coordinator at the Electronic Frontier Foundation in San Francisco, said Google's rejection of government demands to censor "changes the game because the question won't be 'How can we work in China?' but 'How can we create services that Chinese people can use, from outside of China?' "

But Clothilde Le Coz, Washington director for Reporters Without Borders, said that Google's move doesn't necessarily mean more information will be available to the average Chinese person.

"The Chinese government is one of the most efficient in terms of censoring the Web," she said. The media watchdog group has long criticized Google and other Internet companies for agreeing to China's demands to censor content.

A spokesman for the Chinese consulate in San Francisco had no immediate comment.

Google, whose headquarters is in Mountain View, Calif., first agreed to censor search results in China in 2006 when it created a version of its search engine bearing China's Web suffix, ".cn."

Previously, Chinese-language results had been available through the company's main Google.com site.

To obtain its Chinese license, Google agreed to omit Web content that the country's government found objectionable. At the time, Google executives said they struggled with how to reconcile the censorship concessions with the company's "don't be evil" motto.

By then, Yahoo Inc. had come under fire for giving Chinese officials information about the online activities of two journalists, who were then arrested, convicted and sentenced to 10-year prison terms for allegedly leaking state secrets and political writings.

Meanwhile, Microsoft Corp. was criticized for shutting down, at Beijing's request, a popular Chinese blog that touches on topics such as press freedoms.