China has blocked Twitter, Hotmail and Flickr, just days before the date when Beijing crushed pro-democracy protests in 1989.
The Twitter Web site would not load in China Tuesday evening, according to people contacted in the country. The BBC is reporting that access to Hotmail and photo sharing site Flikr has been cut.
Twitter users began posting messages about problems accessing the site or its application programming interface (API) address late yesterday afternoon. Applications that let users post Twitter messages without visiting the Web site require access to its API.
Some Chinese dissidents had appeared in recent months on Twitter, which provided a platform for free speech compared to the heavily patrolled blog services in China.
Twenty years ago on Thursday, hundreds died after Beijing ordered soldiers into its central Tiananmen Square to suppress peaceful demonstrations for democracy. China has stepped up monitoring of known dissidents ahead of the anniversary to prevent any public disturbances.