Chinese hackers have accessed the accounts of hundreds of Gmail users, including senior US officials, Chinese political activists, military personnel, journalists and officials in several Asian countries, Google has said.
Phishing attack detected
The phishing attack, which originated in Jinan, China, was uncovered through the company's cloud-based security and abuse detection systems.
The aim was to monitor the contents of these users' e-mails, with the perpetrators apparently using stolen passwords to change peoples' forwarding and delegation settings, said the company in a blog post.
"Google detected and has disrupted this campaign to take users' passwords and monitor their e-mails. We have notified victims and secured their accounts. In addition, we have notified the relevant government authorities.
"It is important to stress that our internal systems have not been affected - these account hijackings were not the result of a security problem with Gmail itself. But we believe that being open about these security issues helps users better protect their information online," it said.
Targeted attack from China
Last year, Google was subject to a highly targeted attack originating in China, which aimed to steal information about human rights activists from the company's Gmail service.
The news is likely to raise suspicions that the attack was coordinated by the Chinese government. According to the Wikileaks diplomatic cable, the US believed China had been hacking into computers belonging to the governments of other Western countries and e-mail accounts used by Chinese dissidents since 2002.