Google has warned its users of possible “state-sponsored” attacks aimed at obtaining vital information by hacking their personal accounts, but has stopped short of naming who it sees as potential hackers.

US intelligence reports have said attacks traced back to Russian and Chinese intelligence services have already stolen vital commercial information. An annual report from Pentagon claimed that China is engaging in “economic espionage” directed at technology and military information. Human rights activists in China are also thought to have been targeted.

Google closed its search engine in China due to strict censorship it said was unacceptable. Rampant attacks targeted personal accounts of people connected with the US government, important businesses and the military. Google added a feature that would warn users once they identify a possible attack, while the company is conducting investigations.

Just last month, staff from several pipeline companies recieved suspicious e-mails, purportedly sent by their colleagues. Reports believe that the hackers are using “phishing” techniques to illegally obtain vital information on US natural gas pipelines.