The attacks on Google email accounts belonging to human rights activists can be traced back to the Chinese government “or its proxies”, according to a US internet security firm.

Verisign’s iDefense Labs claims the web addresses involved in the cyber-attack “correspond to a single foreign entity consisting either of agents of the Chinese state or proxies thereof”, reports The Guardian.

The newspaper said researchers at the security firm have managed to find a link to the computer servers which controlled software used by the hackers. The company has also spoken to “several sources” which Verisign says have backed up its claims.

Earlier this week Google went public with news of the attacks, and said it is considering pulling out of the country and ceasing its business operations in China. The search giant, which began operating in China in 2006, said it is no longer prepared to censor internet results in order to comply with Chinese law.

In response, China said it intends to stand firm over censorship of certain internet content and that media companies must “live up to their responsibility of maintaining internet security”, which includes censoring content.