The Vietnamese government claims it only wants to deny access to online pornography, but it is actually far more interested in blocking access to political and religious websites.

So says a report into online censorship in Vietnam by the OpenNet Initiative, a group of researchers from Harvard, Oxford, Cambridge and Toronto universities. The report, published last week, says the government is using increasingly sophisticated filtering techniques to block access to sites that could threaten the country's one-party system, on topics such as political dissidents, democracy and Buddhism.

Sites written in Vietnamese are far more likely to be blocked than those in English. Internet usage in cybercafes, the most common way to access the web in Vietnam, is checked regularly, the report says.