On the eve of the 20th anniversary of the Tiananmen Square revolt, China is censoring information about the demonstrations on the Internet.

Reporters Without Borders said this week that Chinese media cannot refer to the incident, which took place June 4, 1989, and information has been suppressed so effectively that most young Chinese are unaware of the event, which led to the deaths of hundreds of demonstrators.

When Internet users look for information on "4 June," Baidu, China's most popular search engine, displays a message saying: "The search does not comply with laws, regulations, and policies," Reporters Without Borders found in recent tests. Video search for the date leads to a message that says, "Sorry, no video corresponds to your search."

There is no information about the protest, which demanded free press, or the government's crackdown on the demonstration, which lasted for weeks.

The Chinese version of Google's search engine appears to block video and photo related to the massacre inside of China, but English-language searches show the events for those searching "4 June" and Chinese-language searches outside of China yield information from the 1989 events as well, Reporter Without Borders found.

YouTube and Wikipedia do not censor the information on their Chinese sites, but those Web sites are blocked within China, the group said.

In 2004, journalist Shi Tao was sentenced to 10 years imprisonment for sending an e-mail about the Tiananmen Square anniversary. Activists from the movement and those who want recognition for victims have also been arrested as recently as last year, according to Reporters Without Borders.

Reporters Without Borders noted that China has changed since the clash over the pro-democracy demonstrations and it wants the Chinese government to release journalists, bloggers, and activists detained for information about the protests to be released. It wants Chinese press and Internet users to be able to exchange information on the events of May and June 1989, and it wants the government to rehabilitate journalists who have been transferred, fired, or forced to retire for supporting the movement.

It has called on the Chinese government to end U.S. Internet companies' censorship of information about the demonstrations and allow foreign journalists to cover dissident activities and events related to the demonstrations.