From BBC 13 January 2010

It said it had found a "sophisticated and targeted attack on our corporate infrastructure originating from China".

It did not specifically accuse China's government but said it was no longer willing to censor its Chinese site's results, as the government requires.

Google said the decision might mean it has to shut the site, set up in 2006.

Phishing scam

Shortly after the news was announced, shares in Google fell by 1.9% to $579 (£358) in after-hours trading in New York.

In a blog post announcing its decision, Google's David Drummond said: "A primary goal of the attackers was accessing the Gmail accounts of Chinese human rights activists."

The company said its investigation into the attack found two Gmail accounts appeared to have been accessed.

However, activity was limited to account information such as the date the account was created and subject line, rather than e-mail content, it said.

It was also discovered the accounts of dozens of US, China and Europe-based Gmail users, who are "advocates of human rights in China", appeared to have been "routinely accessed by third parties".

It said these accounts had not been accessed through any security breach at Google, but "most likely via phishing scams or malware placed on users' computers".

At least 20 other large companies from a wide range of businesses were similarly targeted, it added.

In the coming weeks, Google said it would hold talks with the Chinese government to look at operating an unfiltered search engine within the law.

The decision, it said, had been "incredibly hard" and driven by company executives in the US, not employees in China.

BBC technology correspondent Rory Cellan Jones said the attacks, coupled with further attempts to limit free speech, had led Google to reconsider its position.

"If, as seems likely, the government refuses to allow it to operate an uncensored service, then Google will pull out.

"That will leave other overseas web companies operating in China with difficult decisions to make," he added.

Google first launched in China four years ago after agreeing to censor some search results.

The move led to accusations it had betrayed its company motto - "don't do evil" but Google argued it would be more damaging for civil liberties if it pulled out of China entirely.

Last summer, Google was at loggerheads with China after it was accused of breaking the law by spreading pornography.