Hackers likely based in China tried to break into hundreds of Google mail accounts, including those of senior US government officials, Chinese activists and journalists, the Internet company said.

The unknown perpetrators, who appeared to originate from the city of Jinan in Shandong province, recently tried to crack and monitor email accounts by stealing passwords, but Google  detected and "disrupted" their campaign, the world's largest Web search company said on its official blog.

The revelation comes more than a year after Google disclosed a cyberattack on its systems that it said it traced to China, and could further strain an already tense relationship between the Web giant and Beijing. Google eventually all but pulled out of the world's largest Internet market by users.

"We recently uncovered a campaign to collect user passwords, likely through phishing," Google said in a post on its corporate blog, referring to the practice where computer users are tricked into giving up sensitive information.

"The goal of this effort seems to have been to monitor the contents of these users' emails."

It "affected what seem to be the personal Gmail accounts of hundreds of users, including among others, senior US
government officials, Chinese political activists, officials in several Asian countries (predominantly South Korea), military personnel and journalists."     

Google did not say the Chinese government was behind the attacks or say what might have motivated the intrusions.

But cyberattacks originating in China have become common in recent years, said Bruce Schneier, chief security technology officer at telecommunications company BT.

"It's not just the Chinese government. It's independent actors within China who are working with the tacit approval of the government," he said.

The events leading to Google's withdrawal from China exacerbated an often difficult relationship between Washington and Beijing, with disputes ranging from human rights to trade. The attacks revealed on Wednesday were also the latest computer-based invasions directed at western companies.

The United States has warned that a cyberattack -- presumably if it is devastating enough -- could result in real-world military retaliation, although analysts say it could be difficult to detect its origin with full accuracy.

Lockheed Martin Corp , the US government's top information technology provider, said last week it had thwarted "a significant and tenacious attack" on its information systems network, though the company and government officials have not yet said where they think the attack originated.

The White House said it was investigating Google's claims. "We have no reason to believe that any official US government email accounts were accessed," said White House spokesman Tommy Vietor.    

The FBI said it was working with Google on the matter. A spokesman at South Korea's presidential office said the Blue House had not been affected, but added they did not use Gmail. South Korea's Ministry of Strategy and Finance said it had warned all staff "not to use send or receive any official information through private emails such as Gmail." 

Jinan, the capital of eastern Shandong province, is the location of one of six technical reconnaissance bureaus belonging to the People's Liberation Army, which oversees China's electronic eavesdropping, according to an October 2009 report by the US-China Economic and Security Commission, a panel created by Congress to monitor potential national security issues related to US- China relations.

The bureaus "are likely focused on defense or exploitation of foreign networks", the commission report states. - Reuters