China blocks Twitter access

China has blocked access to social-networking services including Twitter ahead of the 20th anniversary of the bloody crackdown on Tiananmen Square.

This Thursday is the anniversary of the massacre, when tanks rolled into Tiananmen Square before dawn to quell weeks of protest by students and workers.

As well as blocking access to Twitter, chat on Chinese forums suggests that services such as Flickr, the photo-sharing website owned by Yahoo and Hotmail, Microsoft's email service, have all been blocked.

Some surfers also report that Bing, the new search engine from Microsoft has also been blocked.

One theory for this is that Bing automatically plays videos when the mouse is hovered over them in the results page.

However, it may also concern the nature of Bing's search results – Google is only allowed to provide a heavily-censored version of its search engine in China.

China classes the events of 4 June as a "counter-revolutionary" conspiracy. The Red Cross said as many as 2,600 people were killed, although Chinese officials have never released an exact figure.

China routinely blocks access to websites which it deems do not conform to levels of decency or which are critical of Chinese policy.