|China has blocked many websites related to human rights and other sensitive issues [EPA]
US diplomatic cables released by WikiLeaks have linked senior Chinese officials to the hacking of Google that led the company to briefly pull out of China earlier this year.
Citing the cables on Saturday, The New York Times newspaper said the country's senior propaganda official had overseen the cyber attack after he had found "results critical of him" when he typed his name into the search engine.
"A well-placed contact claims that the Chinese government co-ordinated the recent intrusions of Google systems," a cable dated earlier this year said.
"According to our contact, the closely held operations were directed at the Politburo Standing Committee level," it said, referring to the ruling body of the Chinese Communist Party.
Google, the world's leading internet search engine, closed its China-based search service in March this year, two months after it had said it would stop censoring search results in response to what it said was a sophisticated cyber attack that it traced to China and increasing limits on freedom of expression.
The cables cited by The New York Times said the attacks were co-ordinated out of the State Council Information Office with the oversight of Li Changchun, the propaganda chief, and Zhou Yongkang, China's top security official.
But the Times said that in an interview with the paper, the "Chinese person with family connections to the elite" cited in the cable had said Li personally oversaw a campaign against Google, but the source denied knowing who directed the attack.
The Times did not explain the discrepancy between what the person said in the interview and what was attributed to the person in the cable.
Al Jazeera's Melissa Chan, reporting from Beijing, said it was impossible to verify the information given by the source quoted in the cable.
"Let's keep in mind that this information about the propaganda chief having googled himself and been unhappy with the result, and thereby decided to attack Google comes from one source in the state department cables," she said.
"The Chinese propaganda chief is one of the most powerful people in the country. If this is true, it would suggest that the attack against Google was known at the highest levels of government."
The cables revealed that China had made repeated and often successful hacking attacks on the US government, private enterprises and Western allies as far back as 2002.
"In the US, the majority of the systems that have been targeted belong to the US army, but targets also include other department of defence services as well as department of state, department of energy, and additional US government entities and networks," a cable said.
According to the cables, at least one previously unreported 2008 attack, which US investigators code-named Byzantine Candor, yielded more than 50 megabytes of email messages along with a complete list of user names and passwords from a US government agency.
The New York Times also said Chinese officials had asked Google to remove material on subjects like the 1989 Tiananmen Square massacre and put pressure on the US government to censor the Google Earth satellite imaging service by lowering the resolution of images of Chinese government facilities.
Last weekend WikiLeaks started publishing what it said were more than 250,000 US diplomatic cables, giving advance access to a number of newspapers.