A number of websites, including Twitter, have questionable status in China. (CBC)

China vowed Tuesday to keep a tight grip on the internet, saying it would continue to block anything considered subversive or threatening to "national unity."

The "white paper" statement of government policy was released three months after a public dispute over censorship prompted Google to shut down its mainland-based search engine.

It said there were 384 million internet users in China at the end of 2009, about 29 per cent of the population. The government aims to boost that to 45 per cent in the next five years by pushing into rural areas where the white paper said there was a "digital gap."

It said the internet had taken an "irreplaceable role in accelerating the development of the national economy" and would continue to impact daily work, education and lifestyles.

'Great Firewall' will not come down

But China, which routinely blocks websites such as Facebook, YouTube and Twitter, gave no sign there would be an easing of the "Great Firewall" — the nickname for the network of filters that keep mainland web surfers from accessing material the government deems sensitive.

The official English translation of the white paper favourably mentions Twitter — an apparent glitch since the U.S. micro-blogging service has been banned in China since last year. The English version named Twitter as an example of a fast-growing service that allows people to express themselves, while the Chinese version mentions only micro-blogs.

The 31-page white paper did not give specific examples of what content would be banned, saying Chinese laws prohibit the spread of "contents subverting state power, undermining national unity, infringing upon national honour and interests, inciting ethnic hatred and secession" as well as such things as pornography and terror.

The white paper also put the onus on companies to block content deemed sensitive, saying China required internet service providers to set up "security management systems and utilize technical measures to prevent the transmission of all types of illegal information."

Google ran afoul of the government when it accused Chinese hackers of trying to plunder its software coding and of hijacking the Gmail accounts of human rights activists, and said it would stop self-censoring its search results in line with Chinese regulations.

It moved its search service to the freer Chinese territory of Hong Kong in March.

The white paper did not mention Google, but said anyone using the internet in China had to respect its laws. "Within Chinese territory the internet is under the jurisdiction of Chinese sovereignty. The internet sovereignty of China should be respected and protected," it said.