China shut down 44,000 web sites and arrested nearly 900 people last year in a campaign to clean up "unhealthy" web content -- a crackdown the nation's Xinhau news agency says will continue until the end of this year's Beijng Olympics. In addition to those arrested, another 1,000 people received unspecified "penalties" for transgressing the nation’s stiff rules on Internet content.

The government says the drive was directed mostly against "pornography", but rights groups were quick to call it a thinly veiled excuse to crack down on political dissidents. President Hu Jintao called the Internet a threat to the nation's social stability.

Since 2005, China has required websites and even individual bloggers to register with the government. According to Xinhua, 200,000 sites were registered last year and 14,000 were refused approval. Independent sources say the real number of rejected applicants is much higher.

In 2006, Google stirred controversy when it announced it would censor its Chinese version to satisfy stiff rules from Beijing, a practice already followed by its competitors Yahoo and Microsoft. In 2007, China forbade the opening of new Internet cafes. The country employs a network of tens of thousands of human "Internet censors", as well as keyword-based firewalls to police online content.

Last month, China announced a ban on video-sharing websites, and said only state-controlled sites would be allowed to post video content online.