BEIJING, CHINA - China said it has ordered 25 websites to stop posting audio-visual content, which comes amid a campaign to censor news about violent unrest in Tibet.

Another 32 websites including the popular video-sharing site tudou.com had received warnings, the State Administration of Radio, Film and Television said in a statement posted on its website on Thursday.

The agency said the websites were being punished for having posted material before February 20 that was obscene, violent or "harmed national security or the national interest."

It was not immediately known why authorities chose the date of February 20, which was well before the outbreak of unrest in Tibet that has been met with a crackdown by Chinese security forces.

The statement did not elaborate on how national security was being threatened or why the punishments were only now being announced.

But China has moved to squelch anything but the officially approved version of the events in Tibet. China says Tibetan "mobs" killed 13 innocent civilians, while Tibetan exiles say close to 100 people were dead in the unrest.

Anti-China protests in the capital Lhasa last week escalated into violent rioting that has since spilled over into Tibetan populated areas of adjacent provinces.

The violence, and subsequent crackdown, has given rise to whispers of an Olympic boycott and mounting calls for China to negotiate with the exiled Tibetan spiritual leader, the Dalai Lama, whom Beijing blames for the unrest.

Foreign journalists have been expelled from Tibet and reporters seeking access to other riot-hit areas have been turned back, and some journalists have reported being threatened by authorities.

Access in China to Youtube has also been blocked for several days since videos of the protests began appearing on the site.

China on January 31 introduced new regulations allowing only state-owned or state-controlled entities to operate websites that post audio-visual material.

The move was widely seen as an expression of growing anxiety about the rapid growth and popularity of online video.

Amid unusually harsh media criticism, the government later said private firms that were in business before the rules and in good standing could continue operations.

With traditional print and broadcast media tightly controlled, such sites often are the only outlet for such sensitive footage as anti-government protests, where they often find a wide audience. --AFP